Merge master into this branch

161 files changed, 4693 insertions, 3359 deletions

diff --git a/src/components/gfx/gfx.rs b/src/components/gfx/gfx.rs
index 5f30e60b4aa..c15d660b934 100644
--- a/src/components/gfx/gfx.rs
+++ b/src/components/gfx/gfx.rs
@@ -54,7 +54,6 @@ pub mod font_context;
 pub mod font_list;
 
 // Misc.
-pub mod opts;
 mod buffer_map;
 
 // Platform-specific implementations.
diff --git a/src/components/gfx/render_context.rs b/src/components/gfx/render_context.rs
index f69c6a29a81..33dd70e87eb 100644
--- a/src/components/gfx/render_context.rs
+++ b/src/components/gfx/render_context.rs
@@ -4,7 +4,6 @@
 
 use font_context::FontContext;
 use style::computed_values::border_style;
-use opts::Opts;
 
 use azure::azure_hl::{B8G8R8A8, Color, ColorPattern, DrawOptions};
 use azure::azure_hl::{DrawSurfaceOptions, DrawTarget, Linear, StrokeOptions};
@@ -18,6 +17,7 @@ use geom::side_offsets::SideOffsets2D;
 use servo_net::image::base::Image;
 use png::{RGBA8, K8, KA8};
 use servo_util::geometry::Au;
+use servo_util::opts::Opts;
 use std::libc::types::common::c99::uint16_t;
 use std::libc::size_t;
 
diff --git a/src/components/gfx/render_task.rs b/src/components/gfx/render_task.rs
index 297c4f5517a..d60a0d84885 100644
--- a/src/components/gfx/render_task.rs
+++ b/src/components/gfx/render_task.rs
@@ -17,6 +17,7 @@ use servo_msg::compositor_msg::{RenderListener, RenderingRenderState};
 use servo_msg::constellation_msg::{ConstellationChan, PipelineId, RendererReadyMsg};
 use servo_msg::constellation_msg::{Failure, FailureMsg};
 use servo_msg::platform::surface::NativeSurfaceAzureMethods;
+use servo_util::opts::Opts;
 use servo_util::time::{ProfilerChan, profile};
 use servo_util::time;
 use servo_util::task::send_on_failure;
@@ -28,7 +29,6 @@ use extra::arc::Arc;
 use buffer_map::BufferMap;
 use display_list::DisplayListCollection;
 use font_context::{FontContext, FontContextInfo};
-use opts::Opts;
 use render_context::RenderContext;
 
 pub struct RenderLayer<T> {
diff --git a/src/components/main/compositing/compositor.rs b/src/components/main/compositing/compositor.rs
index 6b6b55254d9..d3f09d823a7 100644
--- a/src/components/main/compositing/compositor.rs
+++ b/src/components/main/compositing/compositor.rs
@@ -23,7 +23,6 @@ use geom::matrix::identity;
 use geom::point::Point2D;
 use geom::rect::Rect;
 use geom::size::Size2D;
-use gfx::opts::Opts;
 use layers::layers::{ContainerLayer, ContainerLayerKind};
 use layers::platform::surface::NativeCompositingGraphicsContext;
 use layers::rendergl;
@@ -34,6 +33,7 @@ use png;
 use servo_msg::compositor_msg::{Blank, Epoch, FinishedLoading, IdleRenderState, LayerBufferSet, ReadyState, RenderState};
 use servo_msg::constellation_msg::{ConstellationChan, ExitMsg, NavigateMsg, ResizedWindowMsg, LoadUrlMsg, PipelineId};
 use servo_msg::constellation_msg;
+use servo_util::opts::Opts;
 use servo_util::time::{profile, ProfilerChan, Timer};
 use servo_util::{time, url};
 use std::comm::Port;
diff --git a/src/components/main/compositing/compositor_task.rs b/src/components/main/compositing/compositor_task.rs
index 6b5e6c9e347..38e43a8824b 100644
--- a/src/components/main/compositing/compositor_task.rs
+++ b/src/components/main/compositing/compositor_task.rs
@@ -12,11 +12,11 @@ use azure::azure_hl::{SourceSurfaceMethods, Color};
 use geom::point::Point2D;
 use geom::rect::Rect;
 use geom::size::Size2D;
-use gfx::opts::Opts;
 use layers::platform::surface::{NativeCompositingGraphicsContext, NativeGraphicsMetadata};
 use servo_msg::compositor_msg::{Epoch, RenderListener, LayerBufferSet, RenderState, ReadyState};
 use servo_msg::compositor_msg::{ScriptListener, Tile};
 use servo_msg::constellation_msg::{ConstellationChan, PipelineId};
+use servo_util::opts::Opts;
 use servo_util::time::ProfilerChan;
 use std::comm::{Chan, SharedChan, Port};
 use std::num::Orderable;
diff --git a/src/components/main/constellation.rs b/src/components/main/constellation.rs
index f03dae64245..aa5f07b844f 100644
--- a/src/components/main/constellation.rs
+++ b/src/components/main/constellation.rs
@@ -7,7 +7,6 @@ use compositing::{CompositorChan, LoadComplete, SetIds, SetLayerClipRect, Shutdo
 use extra::url::Url;
 use geom::rect::Rect;
 use geom::size::Size2D;
-use gfx::opts::Opts;
 use gfx::render_task;
 use pipeline::{Pipeline, CompositionPipeline};
 use script::script_task::{ResizeMsg, ResizeInactiveMsg, ExitPipelineMsg};
@@ -21,6 +20,7 @@ use servo_msg::constellation_msg;
 use servo_net::image_cache_task::{ImageCacheTask, ImageCacheTaskClient};
 use servo_net::resource_task::ResourceTask;
 use servo_net::resource_task;
+use servo_util::opts::Opts;
 use servo_util::time::ProfilerChan;
 use servo_util::url::parse_url;
 use servo_util::task::spawn_named;
diff --git a/src/components/main/css/matching.rs b/src/components/main/css/matching.rs
index 0f56c74fdfc..0dd4299e5d4 100644
--- a/src/components/main/css/matching.rs
+++ b/src/components/main/css/matching.rs
@@ -5,12 +5,14 @@
 // High-level interface to CSS selector matching.
 
 use css::node_style::StyledNode;
+use layout::construct::FlowConstructor;
+use layout::context::LayoutContext;
 use layout::extra::LayoutAuxMethods;
 use layout::util::{LayoutDataAccess, LayoutDataWrapper};
-use layout::wrapper::{LayoutElement, LayoutNode};
+use layout::wrapper::{LayoutElement, LayoutNode, PostorderNodeMutTraversal, ThreadSafeLayoutNode};
 
 use extra::arc::Arc;
-use script::layout_interface::LayoutChan;
+use gfx::font_context::FontContext;
 use servo_util::cache::{Cache, LRUCache, SimpleHashCache};
 use servo_util::namespace::Null;
 use servo_util::smallvec::{SmallVec, SmallVec0, SmallVec16};
@@ -280,15 +282,17 @@ pub enum StyleSharingResult<'ln> {
 }
 
 pub trait MatchMethods {
-    /// Performs aux initialization, selector matching, and cascading sequentially.
-    fn match_and_cascade_subtree(&self,
-                                 stylist: &Stylist,
-                                 layout_chan: &LayoutChan,
-                                 applicable_declarations: &mut ApplicableDeclarations,
-                                 initial_values: &ComputedValues,
-                                 applicable_declarations_cache: &mut ApplicableDeclarationsCache,
-                                 style_sharing_candidate_cache: &mut StyleSharingCandidateCache,
-                                 parent: Option<LayoutNode>);
+    /// Performs aux initialization, selector matching, cascading, and flow construction
+    /// sequentially.
+    fn recalc_style_for_subtree(&self,
+                                stylist: &Stylist,
+                                layout_context: &mut LayoutContext,
+                                mut font_context: ~FontContext,
+                                applicable_declarations: &mut ApplicableDeclarations,
+                                applicable_declarations_cache: &mut ApplicableDeclarationsCache,
+                                style_sharing_candidate_cache: &mut StyleSharingCandidateCache,
+                                parent: Option<LayoutNode>)
+                                -> ~FontContext;
 
     fn match_node(&self,
                   stylist: &Stylist,
@@ -381,7 +385,7 @@ impl<'ln> PrivateMatchMethods for LayoutNode<'ln> {
         assert!(self.is_element());
 
         let parent_node = match parent_node {
-            Some(parent_node) if parent_node.is_element() => parent_node,
+            Some(ref parent_node) if parent_node.is_element() => parent_node,
             Some(_) | None => return None,
         };
 
@@ -455,7 +459,7 @@ impl<'ln> MatchMethods for LayoutNode<'ln> {
         }
 
         for (i, &(ref candidate, ())) in style_sharing_candidate_cache.iter().enumerate() {
-            match self.share_style_with_candidate_if_possible(parent, candidate) {
+            match self.share_style_with_candidate_if_possible(parent.clone(), candidate) {
                 Some(shared_style) => {
                     // Yay, cache hit. Share the style.
                     let mut layout_data_ref = self.mutate_layout_data();
@@ -474,19 +478,20 @@ impl<'ln> MatchMethods for LayoutNode<'ln> {
         CannotShare(true)
     }
 
-    fn match_and_cascade_subtree(&self,
-                                 stylist: &Stylist,
-                                 layout_chan: &LayoutChan,
-                                 applicable_declarations: &mut ApplicableDeclarations,
-                                 initial_values: &ComputedValues,
-                                 applicable_declarations_cache: &mut ApplicableDeclarationsCache,
-                                 style_sharing_candidate_cache: &mut StyleSharingCandidateCache,
-                                 parent: Option<LayoutNode>) {
-        self.initialize_layout_data((*layout_chan).clone());
+    fn recalc_style_for_subtree(&self,
+                                stylist: &Stylist,
+                                layout_context: &mut LayoutContext,
+                                mut font_context: ~FontContext,
+                                applicable_declarations: &mut ApplicableDeclarations,
+                                applicable_declarations_cache: &mut ApplicableDeclarationsCache,
+                                style_sharing_candidate_cache: &mut StyleSharingCandidateCache,
+                                parent: Option<LayoutNode>)
+                                -> ~FontContext {
+        self.initialize_layout_data(layout_context.layout_chan.clone());
 
         // First, check to see whether we can share a style with someone.
         let sharing_result = unsafe {
-            self.share_style_if_possible(style_sharing_candidate_cache, parent)
+            self.share_style_if_possible(style_sharing_candidate_cache, parent.clone())
         };
 
         // Otherwise, match and cascade selectors.
@@ -497,6 +502,7 @@ impl<'ln> MatchMethods for LayoutNode<'ln> {
                 }
 
                 unsafe {
+                    let initial_values = layout_context.initial_css_values.get();
                     self.cascade_node(parent,
                                       initial_values,
                                       applicable_declarations,
@@ -514,14 +520,20 @@ impl<'ln> MatchMethods for LayoutNode<'ln> {
         }
 
         for kid in self.children() {
-            kid.match_and_cascade_subtree(stylist,
-                                          layout_chan,
-                                          applicable_declarations,
-                                          initial_values,
-                                          applicable_declarations_cache,
-                                          style_sharing_candidate_cache,
-                                          Some(*self))
+            font_context = kid.recalc_style_for_subtree(stylist,
+                                                        layout_context,
+                                                        font_context,
+                                                        applicable_declarations,
+                                                        applicable_declarations_cache,
+                                                        style_sharing_candidate_cache,
+                                                        Some(self.clone()))
         }
+
+        // Construct flows.
+        let layout_node = ThreadSafeLayoutNode::new(self);
+        let mut flow_constructor = FlowConstructor::new(layout_context, Some(font_context));
+        flow_constructor.process(&layout_node);
+        flow_constructor.unwrap_font_context().unwrap()
     }
 
     unsafe fn cascade_node(&self,
diff --git a/src/components/main/css/node_util.rs b/src/components/main/css/node_util.rs
index 7493281d5cc..a14c2901452 100644
--- a/src/components/main/css/node_util.rs
+++ b/src/components/main/css/node_util.rs
@@ -12,10 +12,10 @@ use style::ComputedValues;
 
 pub trait NodeUtil {
     fn get_css_select_results<'a>(&'a self) -> &'a Arc<ComputedValues>;
-    fn have_css_select_results(self) -> bool;
+    fn have_css_select_results(&self) -> bool;
 
-    fn get_restyle_damage(self) -> RestyleDamage;
-    fn set_restyle_damage(self, damage: RestyleDamage);
+    fn get_restyle_damage(&self) -> RestyleDamage;
+    fn set_restyle_damage(&self, damage: RestyleDamage);
 }
 
 impl<'ln> NodeUtil for ThreadSafeLayoutNode<'ln> {
@@ -36,14 +36,14 @@ impl<'ln> NodeUtil for ThreadSafeLayoutNode<'ln> {
     }
 
     /// Does this node have a computed style yet?
-    fn have_css_select_results(self) -> bool {
+    fn have_css_select_results(&self) -> bool {
         let layout_data_ref = self.borrow_layout_data();
         layout_data_ref.get().get_ref().data.style.is_some()
     }
 
     /// Get the description of how to account for recent style changes.
     /// This is a simple bitfield and fine to copy by value.
-    fn get_restyle_damage(self) -> RestyleDamage {
+    fn get_restyle_damage(&self) -> RestyleDamage {
         // For DOM elements, if we haven't computed damage yet, assume the worst.
         // Other nodes don't have styles.
         let default = if self.node_is_element() {
@@ -63,7 +63,7 @@ impl<'ln> NodeUtil for ThreadSafeLayoutNode<'ln> {
     }
 
     /// Set the restyle damage field.
-    fn set_restyle_damage(self, damage: RestyleDamage) {
+    fn set_restyle_damage(&self, damage: RestyleDamage) {
         let mut layout_data_ref = self.mutate_layout_data();
         match *layout_data_ref.get() {
             Some(ref mut layout_data) => layout_data.data.restyle_damage = Some(damage.to_int()),
diff --git a/src/components/main/layout/block.rs b/src/components/main/layout/block.rs
index 607a85c2b7b..079654658b9 100644
--- a/src/components/main/layout/block.rs
+++ b/src/components/main/layout/block.rs
@@ -68,10 +68,10 @@ pub struct BlockFlow {
 }
 
 impl BlockFlow {
-    pub fn from_node(constructor: &mut FlowConstructor, node: ThreadSafeLayoutNode, is_fixed: bool)
+    pub fn from_node(constructor: &mut FlowConstructor, node: &ThreadSafeLayoutNode, is_fixed: bool)
                      -> BlockFlow {
         BlockFlow {
-            base: BaseFlow::new(constructor.next_flow_id(), node),
+            base: BaseFlow::new((*node).clone()),
             box_: Some(Box::new(constructor, node)),
             is_root: false,
             is_fixed: is_fixed,
@@ -80,11 +80,11 @@ impl BlockFlow {
     }
 
     pub fn float_from_node(constructor: &mut FlowConstructor,
-                           node: ThreadSafeLayoutNode,
+                           node: &ThreadSafeLayoutNode,
                            float_type: FloatType)
                            -> BlockFlow {
         BlockFlow {
-            base: BaseFlow::new(constructor.next_flow_id(), node),
+            base: BaseFlow::new((*node).clone()),
             box_: Some(Box::new(constructor, node)),
             is_root: false,
             is_fixed: false,
@@ -688,13 +688,12 @@ impl Flow for BlockFlow {
     /// Dual boxes consume some width first, and the remainder is assigned to all child (block)
     /// contexts.
     fn assign_widths(&mut self, ctx: &mut LayoutContext) {
-        debug!("assign_widths({}): assigning width for flow {}",
+        debug!("assign_widths({}): assigning width for flow",
                if self.is_float() {
                    "float"
                } else {
                    "block"
-               },
-               self.base.id);
+               });
 
         if self.is_root {
             debug!("Setting root position");
@@ -803,10 +802,10 @@ impl Flow for BlockFlow {
 
     fn assign_height_inorder(&mut self, ctx: &mut LayoutContext) {
         if self.is_float() {
-            debug!("assign_height_inorder_float: assigning height for float {}", self.base.id);
+            debug!("assign_height_inorder_float: assigning height for float");
             self.assign_height_float_inorder();
         } else {
-            debug!("assign_height_inorder: assigning height for block {}", self.base.id);
+            debug!("assign_height_inorder: assigning height for block");
             self.assign_height_block_base(ctx, true);
         }
     }
@@ -818,10 +817,10 @@ impl Flow for BlockFlow {
         }
 
         if self.is_float() {
-            debug!("assign_height_float: assigning height for float {}", self.base.id);
+            debug!("assign_height_float: assigning height for float");
             self.assign_height_float(ctx);
         } else {
-            debug!("assign_height: assigning height for block {}", self.base.id);
+            debug!("assign_height: assigning height for block");
             // This is the only case in which a block flow can start an inorder
             // subtraversal.
             if self.is_root && self.base.num_floats > 0 {
diff --git a/src/components/main/layout/box_.rs b/src/components/main/layout/box_.rs
index d0386cdb48a..ff6ccaf93b6 100644
--- a/src/components/main/layout/box_.rs
+++ b/src/components/main/layout/box_.rs
@@ -384,9 +384,9 @@ def_noncontent_horiz!(right, merge_noncontent_inline_right, clear_noncontent_inl
 
 impl Box {
     /// Constructs a new `Box` instance.
-    pub fn new(constructor: &mut FlowConstructor, node: ThreadSafeLayoutNode) -> Box {
+    pub fn new(constructor: &mut FlowConstructor, node: &ThreadSafeLayoutNode) -> Box {
         Box {
-            node: OpaqueNode::from_thread_safe_layout_node(&node),
+            node: OpaqueNode::from_thread_safe_layout_node(node),
             style: node.style().clone(),
             border_box: RefCell::new(Au::zero_rect()),
             border: RefCell::new(Zero::zero()),
diff --git a/src/components/main/layout/construct.rs b/src/components/main/layout/construct.rs
index 41b38577599..0b43884c01f 100644
--- a/src/components/main/layout/construct.rs
+++ b/src/components/main/layout/construct.rs
@@ -27,17 +27,20 @@ use layout::box_::{InlineInfo, InlineParentInfo, SpecificBoxInfo, UnscannedTextB
 use layout::box_::{UnscannedTextBoxInfo};
 use layout::context::LayoutContext;
 use layout::float_context::FloatType;
-use layout::flow::{Flow, FlowLeafSet, ImmutableFlowUtils, MutableOwnedFlowUtils};
+use layout::flow::{Flow, MutableOwnedFlowUtils};
 use layout::inline::InlineFlow;
 use layout::text::TextRunScanner;
 use layout::util::{LayoutDataAccess, OpaqueNode};
 use layout::wrapper::{PostorderNodeMutTraversal, TLayoutNode, ThreadSafeLayoutNode};
 
 use gfx::font_context::FontContext;
+use script::dom::bindings::codegen::InheritTypes::TextCast;
+use script::dom::bindings::js::JS;
 use script::dom::element::{HTMLIframeElementTypeId, HTMLImageElementTypeId, HTMLObjectElementTypeId};
 use script::dom::node::{CommentNodeTypeId, DoctypeNodeTypeId, DocumentFragmentNodeTypeId};
 use script::dom::node::{DocumentNodeTypeId, ElementNodeTypeId, ProcessingInstructionNodeTypeId};
 use script::dom::node::{TextNodeTypeId};
+use script::dom::text::Text;
 use style::computed_values::{display, position, float, white_space};
 use style::ComputedValues;
 use servo_util::namespace;
@@ -47,8 +50,6 @@ use servo_util::str::is_whitespace;
 
 use extra::url::Url;
 use extra::arc::Arc;
-
-use std::cell::RefCell;
 use std::util;
 use std::num::Zero;
 
@@ -68,11 +69,11 @@ pub enum ConstructionResult {
 }
 
 impl ConstructionResult {
-    fn destroy(&mut self, leaf_set: &FlowLeafSet) {
+    fn destroy(&mut self) {
         match *self {
             NoConstructionResult => {}
-            FlowConstructionResult(ref mut flow) => flow.destroy(leaf_set),
-            ConstructionItemConstructionResult(ref mut item) => item.destroy(leaf_set),
+            FlowConstructionResult(ref mut flow) => flow.destroy(),
+            ConstructionItemConstructionResult(ref mut item) => item.destroy(),
         }
     }
 }
@@ -88,12 +89,12 @@ enum ConstructionItem {
 }
 
 impl ConstructionItem {
-    fn destroy(&mut self, leaf_set: &FlowLeafSet) {
+    fn destroy(&mut self) {
         match *self {
             InlineBoxesConstructionItem(ref mut result) => {
                 for splits in result.splits.mut_iter() {
                     for split in splits.mut_iter() {
-                        split.destroy(leaf_set)
+                        split.destroy()
                     }
                 }
             }
@@ -146,8 +147,8 @@ struct InlineBlockSplit {
 }
 
 impl InlineBlockSplit {
-    fn destroy(&mut self, leaf_set: &FlowLeafSet) {
-        self.flow.destroy(leaf_set)
+    fn destroy(&mut self) {
+        self.flow.destroy()
     }
 }
 
@@ -219,59 +220,66 @@ pub struct FlowConstructor<'a> {
     /// The layout context.
     layout_context: &'a mut LayoutContext,
 
-    /// The next flow ID to assign.
+    /// An optional font context. If this is `None`, then we fetch the font context from the
+    /// layout context.
     ///
-    /// FIXME(pcwalton): This is going to have to be atomic; can't we do something better?
-    next_flow_id: RefCell<int>,
-
-    /// The font context.
-    font_context: ~FontContext,
-
-    /// The URL of the page.
-    url: &'a Url, 
+    /// FIXME(pcwalton): This is pretty bogus and is basically just a workaround for libgreen
+    /// having slow TLS.
+    font_context: Option<~FontContext>,
 }
 
-impl<'fc> FlowConstructor<'fc> {
+impl<'a> FlowConstructor<'a> {
     /// Creates a new flow constructor.
-    pub fn init<'a>(layout_context: &'a mut LayoutContext, url: &'a Url) -> FlowConstructor<'a> {
-        let font_context = ~FontContext::new(layout_context.font_context_info.clone());
+    pub fn new(layout_context: &'a mut LayoutContext, font_context: Option<~FontContext>)
+               -> FlowConstructor<'a> {
         FlowConstructor {
             layout_context: layout_context,
-            next_flow_id: RefCell::new(0),
             font_context: font_context,
-            url: url,
         }
     }
 
-    /// Returns the next flow ID and bumps the internal counter.
-    pub fn next_flow_id(&self) -> int {
-        let id = self.next_flow_id.get();
-        self.next_flow_id.set(id + 1);
-        id
+    fn font_context<'a>(&'a mut self) -> &'a mut FontContext {
+        match self.font_context {
+            Some(ref mut font_context) => {
+                let font_context: &mut FontContext = *font_context;
+                font_context
+            }
+            None => self.layout_context.font_context(),
+        }
+    }
+
+    /// Destroys this flow constructor and retrieves the font context.
+    pub fn unwrap_font_context(self) -> Option<~FontContext> {
+        let FlowConstructor {
+            font_context,
+            ..
+        } = self;
+        font_context
     }
 
     /// Builds the `ImageBoxInfo` for the given image. This is out of line to guide inlining.
-    fn build_box_info_for_image(&mut self, node: ThreadSafeLayoutNode, url: Option<Url>) -> SpecificBoxInfo {
+    fn build_box_info_for_image(&mut self, node: &ThreadSafeLayoutNode, url: Option<Url>) -> SpecificBoxInfo {
         match url {
             None => GenericBox,
             Some(url) => {
                 // FIXME(pcwalton): The fact that image boxes store the cache within them makes
                 // little sense to me.
-                ImageBox(ImageBoxInfo::new(&node, url, self.layout_context.image_cache.clone()))
+                ImageBox(ImageBoxInfo::new(node, url, self.layout_context.image_cache.clone()))
             }
         }
     }
 
     /// Builds specific `Box` info for the given node.
-    pub fn build_specific_box_info_for_node(&mut self, node: ThreadSafeLayoutNode)
+    pub fn build_specific_box_info_for_node(&mut self, node: &ThreadSafeLayoutNode)
                                             -> SpecificBoxInfo {
         match node.type_id() {
             ElementNodeTypeId(HTMLImageElementTypeId) => self.build_box_info_for_image(node, node.image_url()),
-            ElementNodeTypeId(HTMLIframeElementTypeId) => IframeBox(IframeBoxInfo::new(&node)),
+            ElementNodeTypeId(HTMLIframeElementTypeId) => IframeBox(IframeBoxInfo::new(node)),
             ElementNodeTypeId(HTMLObjectElementTypeId) => {
-                self.build_box_info_for_image(node, node.get_object_data(self.url))
+                let data = node.get_object_data(&self.layout_context.url);
+                self.build_box_info_for_image(node, data)
             }
-            TextNodeTypeId => UnscannedTextBox(UnscannedTextBoxInfo::new(&node)),
+            TextNodeTypeId => UnscannedTextBox(UnscannedTextBoxInfo::new(node)),
             _ => GenericBox,
         }
     }
@@ -284,14 +292,14 @@ impl<'fc> FlowConstructor<'fc> {
     fn flush_inline_boxes_to_flow(&mut self,
                                   boxes: ~[Box],
                                   flow: &mut ~Flow,
-                                  node: ThreadSafeLayoutNode) {
+                                  node: &ThreadSafeLayoutNode) {
         if boxes.len() == 0 {
             return
         }
 
-        let mut inline_flow = ~InlineFlow::from_boxes(self.next_flow_id(), node, boxes) as ~Flow;
-        inline_flow.mark_as_leaf(self.layout_context.flow_leaf_set.get());
-        TextRunScanner::new().scan_for_runs(self.font_context, inline_flow);
+        let mut inline_flow = ~InlineFlow::from_boxes((*node).clone(), boxes) as ~Flow;
+        TextRunScanner::new().scan_for_runs(self.font_context(), inline_flow);
+        inline_flow.finish(self.layout_context);
 
         flow.add_new_child(inline_flow)
     }
@@ -301,7 +309,7 @@ impl<'fc> FlowConstructor<'fc> {
     fn flush_inline_boxes_to_flow_if_necessary(&mut self,
                                                opt_boxes: &mut Option<~[Box]>,
                                                flow: &mut ~Flow,
-                                               node: ThreadSafeLayoutNode) {
+                                               node: &ThreadSafeLayoutNode) {
         let opt_boxes = util::replace(opt_boxes, None);
         if opt_boxes.len() > 0 {
             self.flush_inline_boxes_to_flow(opt_boxes.to_vec(), flow, node)
@@ -311,7 +319,7 @@ impl<'fc> FlowConstructor<'fc> {
     /// Builds the children flows underneath a node with `display: block`. After this call,
     /// other `BlockFlow`s or `InlineFlow`s will be populated underneath this node, depending on
     /// whether {ib} splits needed to happen.
-    fn build_children_of_block_flow(&mut self, flow: &mut ~Flow, node: ThreadSafeLayoutNode) {
+    fn build_children_of_block_flow(&mut self, flow: &mut ~Flow, node: &ThreadSafeLayoutNode) {
         // Gather up boxes for the inline flows we might need to create.
         let mut opt_boxes_for_inline_flow = None;
         let mut first_box = true;
@@ -396,17 +404,13 @@ impl<'fc> FlowConstructor<'fc> {
                                                      node);
 
         // The flow is done. If it ended up with no kids, add the flow to the leaf set.
-        if flow.child_count() == 0 {
-            flow.mark_as_leaf(self.layout_context.flow_leaf_set.get())
-        } else {
-            flow.mark_as_nonleaf()
-        }
+        flow.finish(self.layout_context)
     }
 
     /// Builds a flow for a node with `display: block`. This yields a `BlockFlow` with possibly
     /// other `BlockFlow`s or `InlineFlow`s underneath it, depending on whether {ib} splits needed
     /// to happen.
-    fn build_flow_for_block(&mut self, node: ThreadSafeLayoutNode, is_fixed: bool) -> ~Flow {
+    fn build_flow_for_block(&mut self, node: &ThreadSafeLayoutNode, is_fixed: bool) -> ~Flow {
         let mut flow = ~BlockFlow::from_node(self, node, is_fixed) as ~Flow;
         self.build_children_of_block_flow(&mut flow, node);
         flow
@@ -414,7 +418,7 @@ impl<'fc> FlowConstructor<'fc> {
 
     /// Builds the flow for a node with `float: {left|right}`. This yields a float `BlockFlow` with
     /// a `BlockFlow` underneath it.
-    fn build_flow_for_floated_block(&mut self, node: ThreadSafeLayoutNode, float_type: FloatType)
+    fn build_flow_for_floated_block(&mut self, node: &ThreadSafeLayoutNode, float_type: FloatType)
                                     -> ~Flow {
         let mut flow = ~BlockFlow::float_from_node(self, node, float_type) as ~Flow;
         self.build_children_of_block_flow(&mut flow, node);
@@ -425,7 +429,7 @@ impl<'fc> FlowConstructor<'fc> {
     /// Concatenates the boxes of kids, adding in our own borders/padding/margins if necessary.
     /// Returns the `InlineBoxesConstructionResult`, if any. There will be no
     /// `InlineBoxesConstructionResult` if this node consisted entirely of ignorable whitespace.
-    fn build_boxes_for_nonreplaced_inline_content(&mut self, node: ThreadSafeLayoutNode)
+    fn build_boxes_for_nonreplaced_inline_content(&mut self, node: &ThreadSafeLayoutNode)
                                                   -> ConstructionResult {
         let mut opt_inline_block_splits = None;
         let mut opt_box_accumulator = None;
@@ -542,10 +546,10 @@ impl<'fc> FlowConstructor<'fc> {
 
     fn set_inline_info_for_inline_child(&mut self,
                                         boxes: &~[&Box],
-                                        parent_node: ThreadSafeLayoutNode) {
+                                        parent_node: &ThreadSafeLayoutNode) {
         let parent_box = Box::new(self, parent_node);
         let font_style = parent_box.font_style();
-        let font_group = self.font_context.get_resolved_font_for_style(&font_style);
+        let font_group = self.font_context().get_resolved_font_for_style(&font_style);
         let (font_ascent,font_descent) = font_group.borrow().with_mut( |fg| {
             fg.fonts[0].borrow().with_mut( |font| {
                 (font.metrics.ascent,font.metrics.descent)
@@ -580,7 +584,7 @@ impl<'fc> FlowConstructor<'fc> {
                             style: parent_box.style.clone(),
                             font_ascent: font_ascent,
                             font_descent: font_descent,
-                            node: OpaqueNode::from_thread_safe_layout_node(&parent_node),
+                            node: OpaqueNode::from_thread_safe_layout_node(parent_node),
                         });
                 },
                 &None => {}
@@ -589,7 +593,7 @@ impl<'fc> FlowConstructor<'fc> {
     }
     /// Creates an `InlineBoxesConstructionResult` for replaced content. Replaced content doesn't
     /// render its children, so this just nukes a child's boxes and creates a `Box`.
-    fn build_boxes_for_replaced_inline_content(&mut self, node: ThreadSafeLayoutNode)
+    fn build_boxes_for_replaced_inline_content(&mut self, node: &ThreadSafeLayoutNode)
                                                -> ConstructionResult {
         for kid in node.children() {
             kid.set_flow_construction_result(NoConstructionResult)
@@ -597,7 +601,7 @@ impl<'fc> FlowConstructor<'fc> {
 
         // If this node is ignorable whitespace, bail out now.
         if node.is_ignorable_whitespace() {
-            let opaque_node = OpaqueNode::from_thread_safe_layout_node(&node);
+            let opaque_node = OpaqueNode::from_thread_safe_layout_node(node);
             return ConstructionItemConstructionResult(WhitespaceConstructionItem(
                 opaque_node,
                 node.style().clone()))
@@ -614,7 +618,7 @@ impl<'fc> FlowConstructor<'fc> {
 
     /// Builds one or more boxes for a node with `display: inline`. This yields an
     /// `InlineBoxesConstructionResult`.
-    fn build_boxes_for_inline(&mut self, node: ThreadSafeLayoutNode) -> ConstructionResult {
+    fn build_boxes_for_inline(&mut self, node: &ThreadSafeLayoutNode) -> ConstructionResult {
         // Is this node replaced content?
         if !node.is_replaced_content() {
             // Go to a path that concatenates our kids' boxes.
@@ -630,7 +634,7 @@ impl<'a> PostorderNodeMutTraversal for FlowConstructor<'a> {
     // `#[inline(always)]` because this is always called from the traversal function and for some
     // reason LLVM's inlining heuristics go awry here.
     #[inline(always)]
-    fn process(&mut self, node: ThreadSafeLayoutNode) -> bool {
+    fn process(&mut self, node: &ThreadSafeLayoutNode) -> bool {
         // Get the `display` property for this node, and determine whether this node is floated.
         let (display, float, position) = match node.type_id() {
             ElementNodeTypeId(_) => {
@@ -641,7 +645,7 @@ impl<'a> PostorderNodeMutTraversal for FlowConstructor<'a> {
             CommentNodeTypeId |
             DoctypeNodeTypeId |
             DocumentFragmentNodeTypeId |
-            DocumentNodeTypeId(_) |
+            DocumentNodeTypeId |
             ProcessingInstructionNodeTypeId => (display::none, float::none, position::static_),
         };
 
@@ -654,7 +658,7 @@ impl<'a> PostorderNodeMutTraversal for FlowConstructor<'a> {
             (display::none, _, _) => {
                 for child in node.children() {
                     let mut old_result = child.swap_out_construction_result();
-                    old_result.destroy(self.layout_context.flow_leaf_set.get())
+                    old_result.destroy()
                 }
             }
 
@@ -693,39 +697,40 @@ impl<'a> PostorderNodeMutTraversal for FlowConstructor<'a> {
 /// A utility trait with some useful methods for node queries.
 trait NodeUtils {
     /// Returns true if this node doesn't render its kids and false otherwise.
-    fn is_replaced_content(self) -> bool;
+    fn is_replaced_content(&self) -> bool;
 
     /// Returns true if this node is ignorable whitespace.
-    fn is_ignorable_whitespace(self) -> bool;
+    fn is_ignorable_whitespace(&self) -> bool;
 
     /// Sets the construction result of a flow.
-    fn set_flow_construction_result(self, result: ConstructionResult);
+    fn set_flow_construction_result(&self, result: ConstructionResult);
 
     /// Replaces the flow construction result in a node with `NoConstructionResult` and returns the
     /// old value.
-    fn swap_out_construction_result(self) -> ConstructionResult;
+    fn swap_out_construction_result(&self) -> ConstructionResult;
 }
 
 impl<'ln> NodeUtils for ThreadSafeLayoutNode<'ln> {
-    fn is_replaced_content(self) -> bool {
+    fn is_replaced_content(&self) -> bool {
         match self.type_id() {
             TextNodeTypeId |
             ProcessingInstructionNodeTypeId |
             CommentNodeTypeId |
             DoctypeNodeTypeId |
             DocumentFragmentNodeTypeId |
-            DocumentNodeTypeId(_) |
+            DocumentNodeTypeId |
             ElementNodeTypeId(HTMLImageElementTypeId) => true,
             ElementNodeTypeId(HTMLObjectElementTypeId) => self.has_object_data(),
             ElementNodeTypeId(_) => false,
         }
     }
 
-    fn is_ignorable_whitespace(self) -> bool {
+    fn is_ignorable_whitespace(&self) -> bool {
         match self.type_id() {
             TextNodeTypeId => {
                 unsafe {
-                    if !self.with_text(|text| is_whitespace(text.characterdata.data)) {
+                    let text: JS<Text> = TextCast::to(self.get_jsmanaged());
+                    if !is_whitespace(text.get().characterdata.data) {
                         return false
                     }
 
@@ -746,7 +751,7 @@ impl<'ln> NodeUtils for ThreadSafeLayoutNode<'ln> {
     }
 
     #[inline(always)]
-    fn set_flow_construction_result(self, result: ConstructionResult) {
+    fn set_flow_construction_result(&self, result: ConstructionResult) {
         let mut layout_data_ref = self.mutate_layout_data();
         match *layout_data_ref.get() {
             Some(ref mut layout_data) => layout_data.data.flow_construction_result = result,
@@ -755,7 +760,7 @@ impl<'ln> NodeUtils for ThreadSafeLayoutNode<'ln> {
     }
 
     #[inline(always)]
-    fn swap_out_construction_result(self) -> ConstructionResult {
+    fn swap_out_construction_result(&self) -> ConstructionResult {
         let mut layout_data_ref = self.mutate_layout_data();
         match *layout_data_ref.get() {
             Some(ref mut layout_data) => {
@@ -769,29 +774,29 @@ impl<'ln> NodeUtils for ThreadSafeLayoutNode<'ln> {
 /// Methods for interacting with HTMLObjectElement nodes
 trait ObjectElement {
     /// Returns None if this node is not matching attributes.
-    fn get_type_and_data(self) -> (Option<&'static str>, Option<&'static str>);
+    fn get_type_and_data(&self) -> (Option<&'static str>, Option<&'static str>);
 
     /// Returns true if this node has object data that is correct uri.
-    fn has_object_data(self) -> bool;
+    fn has_object_data(&self) -> bool;
 
     /// Returns the "data" attribute value parsed as a URL    
-    fn get_object_data(self, base_url: &Url) -> Option<Url>;
+    fn get_object_data(&self, base_url: &Url) -> Option<Url>;
 }
 
 impl<'ln> ObjectElement for ThreadSafeLayoutNode<'ln> {
-    fn get_type_and_data(self) -> (Option<&'static str>, Option<&'static str>) {
+    fn get_type_and_data(&self) -> (Option<&'static str>, Option<&'static str>) {
         (self.with_element(|e| { e.get_attr(&namespace::Null, "type") } ),
         self.with_element(|e| { e.get_attr(&namespace::Null, "data") } ))
     }
 
-    fn has_object_data(self) -> bool {
+    fn has_object_data(&self) -> bool {
         match self.get_type_and_data() {
             (None, Some(uri)) => is_image_data(uri),
             _ => false
         }   
     }
 
-    fn get_object_data(self, base_url: &Url) -> Option<Url> {
+    fn get_object_data(&self, base_url: &Url) -> Option<Url> {
         match self.get_type_and_data() {
             (None, Some(uri)) if is_image_data(uri) => Some(parse_url(uri, Some(base_url.clone()))),
             _ => None
diff --git a/src/components/main/layout/context.rs b/src/components/main/layout/context.rs
index 61b8c3e03e6..d2ce78bd3d8 100644
--- a/src/components/main/layout/context.rs
+++ b/src/components/main/layout/context.rs
@@ -5,11 +5,10 @@
 //! Data needed by the layout task.
 
 use css::matching::{ApplicableDeclarationsCache, StyleSharingCandidateCache};
-use layout::flow::FlowLeafSet;
 use layout::util::OpaqueNode;
-use layout::wrapper::DomLeafSet;
 
 use extra::arc::{Arc, MutexArc};
+use extra::url::Url;
 use geom::size::Size2D;
 use gfx::font_context::{FontContext, FontContextInfo};
 use green::task::GreenTask;
@@ -17,6 +16,7 @@ use script::layout_interface::LayoutChan;
 use servo_msg::constellation_msg::ConstellationChan;
 use servo_net::local_image_cache::LocalImageCache;
 use servo_util::geometry::Au;
+use servo_util::opts::Opts;
 use std::cast;
 use std::ptr;
 use std::rt::Runtime;
@@ -47,15 +47,9 @@ pub struct LayoutContext {
     /// A channel up to the constellation.
     constellation_chan: ConstellationChan,
 
-    /// The set of leaf DOM nodes.
-    dom_leaf_set: Arc<DomLeafSet>,
-
     /// A channel up to the layout task.
     layout_chan: LayoutChan,
 
-    /// The set of leaf flows.
-    flow_leaf_set: Arc<FlowLeafSet>,
-
     /// Information needed to construct a font context.
     font_context_info: FontContextInfo,
 
@@ -69,18 +63,26 @@ pub struct LayoutContext {
 
     /// The root node at which we're starting the layout.
     reflow_root: OpaqueNode,
+
+    /// The URL.
+    url: Url,
+
+    /// The command line options.
+    opts: Opts,
 }
 
 impl LayoutContext {
     pub fn font_context<'a>(&'a mut self) -> &'a mut FontContext {
         // Sanity check.
-        let mut task = Local::borrow(None::<Task>);
-        match task.get().maybe_take_runtime::<GreenTask>() {
-            Some(green) => {
-                task.get().put_runtime(green as ~Runtime);
-                fail!("can't call this on a green task!")
+        {
+            let mut task = Local::borrow(None::<Task>);
+            match task.get().maybe_take_runtime::<GreenTask>() {
+                Some(green) => {
+                    task.get().put_runtime(green as ~Runtime);
+                    fail!("can't call this on a green task!")
+                }
+                None => {}
             }
-            None => {}
         }
 
         unsafe {
diff --git a/src/components/main/layout/extra.rs b/src/components/main/layout/extra.rs
index ba7cf8a2595..a5724aaabcd 100644
--- a/src/components/main/layout/extra.rs
+++ b/src/components/main/layout/extra.rs
@@ -10,15 +10,15 @@ use script::layout_interface::LayoutChan;
 
 /// Functionality useful for querying the layout-specific data on DOM nodes.
 pub trait LayoutAuxMethods {
-    fn initialize_layout_data(self, chan: LayoutChan);
-    fn initialize_style_for_subtree(self, chan: LayoutChan);
+    fn initialize_layout_data(&self, chan: LayoutChan);
+    fn initialize_style_for_subtree(&self, chan: LayoutChan);
 }
 
 impl<'ln> LayoutAuxMethods for LayoutNode<'ln> {
     /// Resets layout data and styles for the node.
     ///
     /// FIXME(pcwalton): Do this as part of box building instead of in a traversal.
-    fn initialize_layout_data(self, chan: LayoutChan) {
+    fn initialize_layout_data(&self, chan: LayoutChan) {
         let mut layout_data_ref = self.mutate_layout_data();
         match *layout_data_ref.get() {
             None => {
@@ -34,7 +34,7 @@ impl<'ln> LayoutAuxMethods for LayoutNode<'ln> {
     /// Resets layout data and styles for a Node tree.
         ///
     /// FIXME(pcwalton): Do this as part of box building instead of in a traversal.
-    fn initialize_style_for_subtree(self, chan: LayoutChan) {
+    fn initialize_style_for_subtree(&self, chan: LayoutChan) {
         for n in self.traverse_preorder() {
             n.initialize_layout_data(chan.clone());
         }
diff --git a/src/components/main/layout/flow.rs b/src/components/main/layout/flow.rs
index 1cc1a1cf075..b4a14a53ad9 100644
--- a/src/components/main/layout/flow.rs
+++ b/src/components/main/layout/flow.rs
@@ -33,7 +33,7 @@ use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
 use layout::float_context::{FloatContext, Invalid};
 use layout::incremental::RestyleDamage;
 use layout::inline::InlineFlow;
-use layout::parallel::{FlowParallelInfo, UnsafeFlow};
+use layout::parallel::FlowParallelInfo;
 use layout::parallel;
 use layout::wrapper::ThreadSafeLayoutNode;
 use layout::flow_list::{FlowList, Link, Rawlink, FlowListIterator, MutFlowListIterator};
@@ -45,7 +45,6 @@ use geom::rect::Rect;
 use gfx::display_list::{ClipDisplayItemClass, DisplayListCollection, DisplayList};
 use layout::display_list_builder::ToGfxColor;
 use gfx::color::Color;
-use servo_util::concurrentmap::{ConcurrentHashMap, ConcurrentHashMapIterator};
 use servo_util::geometry::Au;
 use std::cast;
 use std::cell::RefCell;
@@ -215,7 +214,7 @@ pub trait MutableFlowUtils {
                           -> bool;
 
     /// Destroys the flow.
-    fn destroy(self, leaf_set: &FlowLeafSet);
+    fn destroy(self);
 }
 
 pub trait MutableOwnedFlowUtils {
@@ -223,15 +222,16 @@ pub trait MutableOwnedFlowUtils {
     /// it's present.
     fn add_new_child(&mut self, new_child: ~Flow);
 
-    /// Marks the flow as a leaf. The flow must not have children and must not be marked as a
-    /// nonleaf.
-    fn mark_as_leaf(&mut self, leaf_set: &FlowLeafSet);
-
-    /// Marks the flow as a nonleaf. The flow must not be marked as a leaf.
-    fn mark_as_nonleaf(&mut self);
+    /// Finishes a flow. Once a flow is finished, no more child flows or boxes may be added to it.
+    /// This will normally run the bubble-widths (minimum and preferred -- i.e. intrinsic -- width)
+    /// calculation, unless the global `bubble_widths_separately` flag is on.
+    ///
+    /// All flows must be finished at some point, or they will not have their intrinsic widths
+    /// properly computed. (This is not, however, a memory safety problem.)
+    fn finish(&mut self, context: &mut LayoutContext);
 
     /// Destroys the flow.
-    fn destroy(&mut self, leaf_set: &FlowLeafSet);
+    fn destroy(&mut self);
 }
 
 pub enum FlowClass {
@@ -455,13 +455,6 @@ bitfield!(FlowFlags, override_overline, set_override_overline, 0b0000_0100)
 // NB: If you update this, you need to update TEXT_DECORATION_OVERRIDE_BITMASK.
 bitfield!(FlowFlags, override_line_through, set_override_line_through, 0b0000_1000)
 
-// Whether this flow is marked as a leaf. Flows marked as leaves must not have any more kids added
-// to them.
-bitfield!(FlowFlags, is_leaf, set_is_leaf, 0b0100_0000)
-
-// Whether this flow is marked as a nonleaf. Flows marked as nonleaves must have children.
-bitfield!(FlowFlags, is_nonleaf, set_is_nonleaf, 0b1000_0000)
-
 // The text alignment for this flow.
 impl FlowFlags {
     #[inline]
@@ -499,9 +492,6 @@ pub struct BaseFlow {
     next_sibling: Link,
     prev_sibling: Rawlink,
 
-    /* TODO (Issue #87): debug only */
-    id: int,
-
     /* layout computations */
     // TODO: min/pref and position are used during disjoint phases of
     // layout; maybe combine into a single enum to save space.
@@ -563,7 +553,7 @@ impl Iterator<@Box> for BoxIterator {
 
 impl BaseFlow {
     #[inline]
-    pub fn new(id: int, node: ThreadSafeLayoutNode) -> BaseFlow {
+    pub fn new(node: ThreadSafeLayoutNode) -> BaseFlow {
         let style = node.style();
         BaseFlow {
             restyle_damage: node.restyle_damage(),
@@ -572,8 +562,6 @@ impl BaseFlow {
             next_sibling: None,
             prev_sibling: Rawlink::none(),
 
-            id: id,
-
             min_width: Au::new(0),
             pref_width: Au::new(0),
             position: Au::zero_rect(),
@@ -740,7 +728,7 @@ impl<'a> MutableFlowUtils for &'a mut Flow {
                           mut index: uint,
                           lists: &RefCell<DisplayListCollection<E>>)
                           -> bool {
-        debug!("Flow: building display list for f{}", base(self).id);
+        debug!("Flow: building display list");
         index = match self.class() {
             BlockFlowClass => self.as_block().build_display_list_block(builder, container_block_size, dirty, index, lists),
             InlineFlowClass => self.as_inline().build_display_list_inline(builder, container_block_size, dirty, index, lists),
@@ -797,18 +785,9 @@ impl<'a> MutableFlowUtils for &'a mut Flow {
     }
 
     /// Destroys the flow.
-    fn destroy(self, leaf_set: &FlowLeafSet) {
-        let is_leaf = {
-            let base = mut_base(self);
-            base.children.len() == 0
-        };
-
-        if is_leaf {
-            leaf_set.remove(self);
-        } else {
-            for kid in child_iter(self) {
-                kid.destroy(leaf_set)
-            }
+    fn destroy(self) {
+        for kid in child_iter(self) {
+            kid.destroy()
         }
 
         mut_base(self).destroyed = true
@@ -824,84 +803,26 @@ impl MutableOwnedFlowUtils for ~Flow {
         }
 
         let base = mut_base(*self);
-        assert!(!base.flags_info.flags.is_leaf());
         base.children.push_back(new_child);
         let _ = base.parallel.children_count.fetch_add(1, Relaxed);
     }
 
-    /// Marks the flow as a leaf. The flow must not have children and must not be marked as a
-    /// nonleaf.
-    fn mark_as_leaf(&mut self, leaf_set: &FlowLeafSet) {
-        {
-            let base = mut_base(*self);
-            if base.flags_info.flags.is_nonleaf() {
-                fail!("attempted to mark a nonleaf flow as a leaf!")
-            }
-            if base.children.len() != 0 {
-                fail!("attempted to mark a flow with children as a leaf!")
-            }
-            base.flags_info.flags.set_is_leaf(true)
-        }
-        let self_borrowed: &Flow = *self;
-        leaf_set.insert(self_borrowed);
-    }
-
-    /// Marks the flow as a nonleaf. The flow must not be marked as a leaf.
-    fn mark_as_nonleaf(&mut self) {
-        let base = mut_base(*self);
-        if base.flags_info.flags.is_leaf() {
-            fail!("attempted to mark a leaf flow as a nonleaf!")
+    /// Finishes a flow. Once a flow is finished, no more child flows or boxes may be added to it.
+    /// This will normally run the bubble-widths (minimum and preferred -- i.e. intrinsic -- width)
+    /// calculation, unless the global `bubble_widths_separately` flag is on.
+    ///
+    /// All flows must be finished at some point, or they will not have their intrinsic widths
+    /// properly computed. (This is not, however, a memory safety problem.)
+    fn finish(&mut self, context: &mut LayoutContext) {
+        if !context.opts.bubble_widths_separately {
+            self.bubble_widths(context)
         }
-        base.flags_info.flags.set_is_nonleaf(true)
-        // We don't check to make sure there are no children as they might be added later.
     }
 
     /// Destroys the flow.
-    fn destroy(&mut self, leaf_set: &FlowLeafSet) {
+    fn destroy(&mut self) {
         let self_borrowed: &mut Flow = *self;
-        self_borrowed.destroy(leaf_set);
+        self_borrowed.destroy();
     }
 }
 
-/// Keeps track of the leaves of the flow tree. This is used to efficiently start bottom-up
-/// parallel traversals.
-pub struct FlowLeafSet {
-    priv set: ConcurrentHashMap<UnsafeFlow,()>,
-}
-
-impl FlowLeafSet {
-    /// Creates a new flow leaf set.
-    pub fn new() -> FlowLeafSet {
-        FlowLeafSet {
-            set: ConcurrentHashMap::with_locks_and_buckets(64, 256),
-        }
-    }
-
-    /// Inserts a newly-created flow into the leaf set.
-    fn insert(&self, flow: &Flow) {
-        self.set.insert(parallel::borrowed_flow_to_unsafe_flow(flow), ());
-    }
-
-    /// Removes a flow from the leaf set. Asserts that the flow was indeed in the leaf set. (This
-    /// invariant is needed for memory safety, as there must always be exactly one leaf set.)
-    fn remove(&self, flow: &Flow) {
-        if !self.contains(flow) {
-            fail!("attempted to remove a flow from the leaf set that wasn't in the set!")
-        }
-        let flow = parallel::borrowed_flow_to_unsafe_flow(flow);
-        self.set.remove(&flow);
-    }
-
-    pub fn contains(&self, flow: &Flow) -> bool {
-        let flow = parallel::borrowed_flow_to_unsafe_flow(flow);
-        self.set.contains_key(&flow)
-    }
-
-    pub fn clear(&self) {
-        self.set.clear()
-    }
-
-    pub fn iter<'a>(&'a self) -> ConcurrentHashMapIterator<'a,UnsafeFlow,()> {
-        self.set.iter()
-    }
-}
diff --git a/src/components/main/layout/inline.rs b/src/components/main/layout/inline.rs
index 8332c7adb7d..e6a2643536f 100644
--- a/src/components/main/layout/inline.rs
+++ b/src/components/main/layout/inline.rs
@@ -84,8 +84,8 @@ impl LineboxScanner {
         self.floats.clone()
     }
 
-    fn reset_scanner(&mut self, flow: &mut InlineFlow) {
-        debug!("Resetting line box scanner's state for flow f{:d}.", flow.base.id);
+    fn reset_scanner(&mut self) {
+        debug!("Resetting line box scanner's state for flow.");
         self.lines = ~[];
         self.new_boxes = ~[];
         self.cur_y = Au::new(0);
@@ -99,7 +99,7 @@ impl LineboxScanner {
     }
 
     pub fn scan_for_lines(&mut self, flow: &mut InlineFlow) {
-        self.reset_scanner(flow);
+        self.reset_scanner();
 
         loop {
             // acquire the next box to lay out from work list or box list
@@ -142,9 +142,8 @@ impl LineboxScanner {
     }
 
     fn swap_out_results(&mut self, flow: &mut InlineFlow) {
-        debug!("LineboxScanner: Propagating scanned lines[n={:u}] to inline flow f{:d}",
-               self.lines.len(),
-               flow.base.id);
+        debug!("LineboxScanner: Propagating scanned lines[n={:u}] to inline flow",
+               self.lines.len());
 
         util::swap(&mut flow.boxes, &mut self.new_boxes);
         util::swap(&mut flow.lines, &mut self.lines);
@@ -466,9 +465,9 @@ pub struct InlineFlow {
 }
 
 impl InlineFlow {
-    pub fn from_boxes(id: int, node: ThreadSafeLayoutNode, boxes: ~[Box]) -> InlineFlow {
+    pub fn from_boxes(node: ThreadSafeLayoutNode, boxes: ~[Box]) -> InlineFlow {
         InlineFlow {
-            base: BaseFlow::new(id, node),
+            base: BaseFlow::new(node),
             boxes: boxes,
             lines: ~[],
             elems: ElementMapping::new(),
@@ -497,9 +496,7 @@ impl InlineFlow {
 
         // TODO(#228): Once we form line boxes and have their cached bounds, we can be smarter and
         // not recurse on a line if nothing in it can intersect the dirty region.
-        debug!("Flow[{:d}]: building display list for {:u} inline boxes",
-               self.base.id,
-               self.boxes.len());
+        debug!("Flow: building display list for {:u} inline boxes", self.boxes.len());
 
         for box_ in self.boxes.iter() {
             let rel_offset: Point2D<Au> = box_.relative_position(container_block_size);
@@ -636,7 +633,7 @@ impl Flow for InlineFlow {
         let mut pref_width = Au::new(0);
 
         for box_ in self.boxes.iter() {
-            debug!("Flow[{:d}]: measuring {:s}", self.base.id, box_.debug_str());
+            debug!("Flow: measuring {:s}", box_.debug_str());
             box_.compute_borders(box_.style());
             let (this_minimum_width, this_preferred_width) =
                 box_.minimum_and_preferred_widths();
@@ -690,7 +687,7 @@ impl Flow for InlineFlow {
     }
 
     fn assign_height(&mut self, _: &mut LayoutContext) {
-        debug!("assign_height_inline: assigning height for flow {}", self.base.id);
+        debug!("assign_height_inline: assigning height for flow");
 
         // Divide the boxes into lines.
         //
diff --git a/src/components/main/layout/layout_task.rs b/src/components/main/layout/layout_task.rs
index f9856724659..2f70d0ea499 100644
--- a/src/components/main/layout/layout_task.rs
+++ b/src/components/main/layout/layout_task.rs
@@ -9,18 +9,17 @@ use css::matching::{ApplicableDeclarations, ApplicableDeclarationsCache, MatchMe
 use css::matching::{StyleSharingCandidateCache};
 use css::select::new_stylist;
 use css::node_style::StyledNode;
-use layout::construct::{FlowConstructionResult, FlowConstructor, NoConstructionResult};
+use layout::construct::{FlowConstructionResult, NoConstructionResult};
 use layout::context::LayoutContext;
 use layout::display_list_builder::{DisplayListBuilder, ToGfxColor};
-use layout::flow::{Flow, FlowLeafSet, ImmutableFlowUtils, MutableFlowUtils, MutableOwnedFlowUtils};
+use layout::flow::{Flow, ImmutableFlowUtils, MutableFlowUtils, MutableOwnedFlowUtils};
 use layout::flow::{PreorderFlowTraversal, PostorderFlowTraversal};
 use layout::flow;
 use layout::incremental::RestyleDamage;
-use layout::parallel::{AssignHeightsAndStoreOverflowTraversalKind, BubbleWidthsTraversalKind};
-use layout::parallel::{UnsafeFlow};
+use layout::parallel::PaddedUnsafeFlow;
 use layout::parallel;
 use layout::util::{LayoutDataAccess, OpaqueNode, LayoutDataWrapper};
-use layout::wrapper::{DomLeafSet, LayoutNode, TLayoutNode, ThreadSafeLayoutNode};
+use layout::wrapper::{LayoutNode, TLayoutNode, ThreadSafeLayoutNode};
 
 use extra::url::Url;
 use extra::arc::{Arc, MutexArc};
@@ -28,24 +27,25 @@ use geom::rect::Rect;
 use geom::size::Size2D;
 use gfx::display_list::{ClipDisplayItemClass, DisplayItem, DisplayItemIterator};
 use gfx::display_list::{DisplayList, DisplayListCollection};
-use gfx::font_context::FontContextInfo;
-use gfx::opts::Opts;
+use gfx::font_context::{FontContext, FontContextInfo};
 use gfx::render_task::{RenderMsg, RenderChan, RenderLayer};
 use gfx::{render_task, color};
+use script::dom::bindings::js::JS;
 use script::dom::event::ReflowEvent;
-use script::dom::node::{ElementNodeTypeId, LayoutDataRef};
+use script::dom::node::{ElementNodeTypeId, LayoutDataRef, Node};
 use script::dom::element::{HTMLBodyElementTypeId, HTMLHtmlElementTypeId};
 use script::layout_interface::{AddStylesheetMsg, ContentBoxQuery};
 use script::layout_interface::{ContentBoxesQuery, ContentBoxesResponse, ExitNowMsg, LayoutQuery};
 use script::layout_interface::{HitTestQuery, ContentBoxResponse, HitTestResponse, MouseOverQuery, MouseOverResponse};
 use script::layout_interface::{ContentChangedDocumentDamage, LayoutChan, Msg, PrepareToExitMsg};
-use script::layout_interface::{QueryMsg, ReapLayoutDataMsg, Reflow, ReflowDocumentDamage, UntrustedNodeAddress};
+use script::layout_interface::{QueryMsg, ReapLayoutDataMsg, Reflow, UntrustedNodeAddress};
 use script::layout_interface::{ReflowForDisplay, ReflowMsg};
 use script::script_task::{ReflowCompleteMsg, ScriptChan, SendEventMsg};
 use servo_msg::constellation_msg::{ConstellationChan, PipelineId, Failure, FailureMsg};
 use servo_net::image_cache_task::{ImageCacheTask, ImageResponseMsg};
 use servo_net::local_image_cache::{ImageResponder, LocalImageCache};
 use servo_util::geometry::Au;
+use servo_util::opts::Opts;
 use servo_util::time::{ProfilerChan, profile};
 use servo_util::time;
 use servo_util::task::send_on_failure;
@@ -86,12 +86,6 @@ pub struct LayoutTask {
     /// The local image cache.
     local_image_cache: MutexArc<LocalImageCache>,
 
-    /// The set of leaves in the DOM tree.
-    dom_leaf_set: Arc<DomLeafSet>,
-
-    /// The set of leaves in the flow tree.
-    flow_leaf_set: Arc<FlowLeafSet>,
-
     /// The size of the viewport.
     screen_size: Size2D<Au>,
 
@@ -104,7 +98,7 @@ pub struct LayoutTask {
     initial_css_values: Arc<ComputedValues>,
 
     /// The workers that we use for parallel operation.
-    parallel_traversal: Option<WorkQueue<*mut LayoutContext,UnsafeFlow>>,
+    parallel_traversal: Option<WorkQueue<*mut LayoutContext,PaddedUnsafeFlow>>,
 
     /// The channel on which messages can be sent to the profiler.
     profiler_chan: ProfilerChan,
@@ -194,12 +188,14 @@ impl<'a> PostorderFlowTraversal for BubbleWidthsTraversal<'a> {
 }
 
 /// The assign-widths traversal. In Gecko this corresponds to `Reflow`.
-struct AssignWidthsTraversal<'a>(&'a mut LayoutContext);
+pub struct AssignWidthsTraversal<'a> {
+    layout_context: &'a mut LayoutContext,
+}
 
 impl<'a> PreorderFlowTraversal for AssignWidthsTraversal<'a> {
     #[inline]
     fn process(&mut self, flow: &mut Flow) -> bool {
-        flow.assign_widths(**self);
+        flow.assign_widths(self.layout_context);
         true
     }
 }
@@ -303,8 +299,6 @@ impl LayoutTask {
             image_cache_task: image_cache_task.clone(),
             local_image_cache: local_image_cache,
             screen_size: screen_size,
-            dom_leaf_set: Arc::new(DomLeafSet::new()),
-            flow_leaf_set: Arc::new(FlowLeafSet::new()),
 
             display_list_collection: None,
             stylist: ~new_stylist(),
@@ -323,7 +317,7 @@ impl LayoutTask {
     }
 
     // Create a layout context for use in building display lists, hit testing, &c.
-    fn build_layout_context(&self, reflow_root: &LayoutNode) -> LayoutContext {
+    fn build_layout_context(&self, reflow_root: &LayoutNode, url: &Url) -> LayoutContext {
         let font_context_info = FontContextInfo {
             backend: self.opts.render_backend,
             needs_font_list: true,
@@ -334,13 +328,13 @@ impl LayoutTask {
             image_cache: self.local_image_cache.clone(),
             screen_size: self.screen_size.clone(),
             constellation_chan: self.constellation_chan.clone(),
-            dom_leaf_set: self.dom_leaf_set.clone(),
-            flow_leaf_set: self.flow_leaf_set.clone(),
             layout_chan: self.chan.clone(),
             font_context_info: font_context_info,
             stylist: &*self.stylist,
             initial_css_values: self.initial_css_values.clone(),
+            url: (*url).clone(),
             reflow_root: OpaqueNode::from_layout_node(reflow_root),
+            opts: self.opts.clone(),
         }
     }
 
@@ -422,17 +416,8 @@ impl LayoutTask {
         self.stylist.add_stylesheet(sheet, AuthorOrigin)
     }
 
-    /// Builds the flow tree.
-    ///
-    /// This corresponds to the various `nsCSSFrameConstructor` methods in Gecko or
-    /// `createRendererIfNeeded` in WebKit. Note, however that in WebKit `createRendererIfNeeded`
-    /// is intertwined with selector matching, making it difficult to compare directly. It is
-    /// marked `#[inline(never)]` to aid benchmarking in sampling profilers.
-    #[inline(never)]
-    fn construct_flow_tree(&self, layout_context: &mut LayoutContext, node: LayoutNode, url: &Url) -> ~Flow {
-        let node = ThreadSafeLayoutNode::new(node);
-        node.traverse_postorder_mut(&mut FlowConstructor::init(layout_context, url));
-
+    /// Retrieves the flow tree root from the root node.
+    fn get_layout_root(&self, node: LayoutNode) -> ~Flow {
         let mut layout_data_ref = node.mutate_layout_data();
         let result = match *layout_data_ref.get() {
             Some(ref mut layout_data) => {
@@ -456,7 +441,7 @@ impl LayoutTask {
     fn solve_constraints(&mut self,
                          layout_root: &mut Flow,
                          layout_context: &mut LayoutContext) {
-        {
+        if layout_context.opts.bubble_widths_separately {
             let mut traversal = BubbleWidthsTraversal {
                 layout_context: layout_context,
             };
@@ -468,7 +453,12 @@ impl LayoutTask {
         // recompute them every time.
         // NOTE: this currently computes borders, so any pruning should separate that operation
         // out.
-        layout_root.traverse_preorder(&mut AssignWidthsTraversal(layout_context));
+        {
+            let mut traversal = AssignWidthsTraversal {
+                layout_context: layout_context,
+            };
+            layout_root.traverse_preorder(&mut traversal);
+        }
 
         // FIXME(pcwalton): Prune this pass as well.
         {
@@ -485,28 +475,24 @@ impl LayoutTask {
     /// benchmarked against those two. It is marked `#[inline(never)]` to aid profiling.
     #[inline(never)]
     fn solve_constraints_parallel(&mut self,
-                                  layout_root: &mut Flow,
+                                  layout_root: &mut ~Flow,
                                   layout_context: &mut LayoutContext) {
+        if layout_context.opts.bubble_widths_separately {
+            let mut traversal = BubbleWidthsTraversal {
+                layout_context: layout_context,
+            };
+            layout_root.traverse_postorder(&mut traversal);
+        }
+
         match self.parallel_traversal {
             None => fail!("solve_contraints_parallel() called with no parallel traversal ready"),
             Some(ref mut traversal) => {
-                parallel::traverse_flow_tree(BubbleWidthsTraversalKind,
-                                             &self.flow_leaf_set,
-                                             self.profiler_chan.clone(),
-                                             layout_context,
-                                             traversal);
-
                 // NOTE: this currently computes borders, so any pruning should separate that
                 // operation out.
-                // TODO(pcwalton): Run this in parallel as well. This will require a bit more work
-                // because this is a top-down traversal, unlike the others.
-                layout_root.traverse_preorder(&mut AssignWidthsTraversal(layout_context));
-
-                parallel::traverse_flow_tree(AssignHeightsAndStoreOverflowTraversalKind,
-                                             &self.flow_leaf_set,
-                                             self.profiler_chan.clone(),
-                                             layout_context,
-                                             traversal);
+                parallel::traverse_flow_tree_preorder(layout_root,
+                                                      self.profiler_chan.clone(),
+                                                      layout_context,
+                                                      traversal);
             }
         }
     }
@@ -527,8 +513,9 @@ impl LayoutTask {
     /// The high-level routine that performs layout tasks.
     fn handle_reflow(&mut self, data: &Reflow) {
         // FIXME: Isolate this transmutation into a "bridge" module.
-        let node: &LayoutNode = unsafe {
-            transmute(&data.document_root)
+        let node: &mut LayoutNode = unsafe {
+            let mut node: JS<Node> = JS::from_trusted_node_address(data.document_root);
+            transmute(&mut node)
         };
 
         debug!("layout: received layout request for: {:s}", data.url.to_str());
@@ -558,45 +545,51 @@ impl LayoutTask {
         self.screen_size = current_screen_size;
 
         // Create a layout context for use throughout the following passes.
-        let mut layout_ctx = self.build_layout_context(node);
+        let mut layout_ctx = self.build_layout_context(node, &data.url);
+
+        // Create a font context, if this is sequential.
+        //
+        // FIXME(pcwalton): This is a pretty bogus thing to do. Essentially this is a workaround
+        // for libgreen having slow TLS.
+        let mut font_context_opt = if self.parallel_traversal.is_none() {
+            Some(~FontContext::new(layout_ctx.font_context_info.clone()))
+        } else {
+            None
+        };
+
+        // Create a font context, if this is sequential.
+        //
+        // FIXME(pcwalton): This is a pretty bogus thing to do. Essentially this is a workaround
+        // for libgreen having slow TLS.
+        let mut font_context_opt = if self.parallel_traversal.is_none() {
+            Some(~FontContext::new(layout_ctx.font_context_info.clone()))
+        } else {
+            None
+        };
 
         let mut layout_root = profile(time::LayoutStyleRecalcCategory,
                                       self.profiler_chan.clone(),
                                       || {
-            // Perform CSS selector matching if necessary.
-            match data.damage.level {
-                ReflowDocumentDamage => {}
-                _ => {
-                    profile(time::LayoutSelectorMatchCategory, self.profiler_chan.clone(), || {
-                        match self.parallel_traversal {
-                            None => {
-                                let mut applicable_declarations = ApplicableDeclarations::new();
-                                let mut applicable_declarations_cache =
-                                    ApplicableDeclarationsCache::new();
-                                let mut style_sharing_candidate_cache =
-                                    StyleSharingCandidateCache::new();
-                                node.match_and_cascade_subtree(self.stylist,
-                                                               &layout_ctx.layout_chan,
-                                                               &mut applicable_declarations,
-                                                               layout_ctx.initial_css_values.get(),
-                                                               &mut applicable_declarations_cache,
-                                                               &mut style_sharing_candidate_cache,
-                                                               None)
-                            }
-                            Some(ref mut traversal) => {
-                                parallel::match_and_cascade_subtree(node,
-                                                                    &mut layout_ctx,
-                                                                    traversal)
-                            }
-                        }
-                    })
+            // Perform CSS selector matching and flow construction.
+            match self.parallel_traversal {
+                None => {
+                    let mut applicable_declarations = ApplicableDeclarations::new();
+                    let mut applicable_declarations_cache = ApplicableDeclarationsCache::new();
+                    let mut style_sharing_candidate_cache = StyleSharingCandidateCache::new();
+                    drop(node.recalc_style_for_subtree(self.stylist,
+                                                       &mut layout_ctx,
+                                                       font_context_opt.take_unwrap(),
+                                                       &mut applicable_declarations,
+                                                       &mut applicable_declarations_cache,
+                                                       &mut style_sharing_candidate_cache,
+                                                       None))
+                }
+                Some(ref mut traversal) => {
+                    parallel::recalc_style_for_subtree(node, &mut layout_ctx, traversal)
                 }
             }
 
-            // Construct the flow tree.
-            profile(time::LayoutTreeBuilderCategory,
-                    self.profiler_chan.clone(),
-                    || self.construct_flow_tree(&mut layout_ctx, *node, &data.url))
+            self.get_layout_root((*node).clone())
         });
 
         // Verification of the flow tree, which ensures that all nodes were either marked as leaves
@@ -622,7 +615,7 @@ impl LayoutTask {
                 }
                 Some(_) => {
                     // Parallel mode.
-                    self.solve_constraints_parallel(layout_root, &mut layout_ctx)
+                    self.solve_constraints_parallel(&mut layout_root, &mut layout_ctx)
                 }
             }
         });
@@ -648,7 +641,7 @@ impl LayoutTask {
                     if child.type_id() == ElementNodeTypeId(HTMLHtmlElementTypeId) || 
                             child.type_id() == ElementNodeTypeId(HTMLBodyElementTypeId) {
                         let element_bg_color = {
-                            let thread_safe_child = ThreadSafeLayoutNode::new(child);
+                            let thread_safe_child = ThreadSafeLayoutNode::new(&child);
                             thread_safe_child.style()
                                              .get()
                                              .resolve_color(thread_safe_child.style()
@@ -683,7 +676,7 @@ impl LayoutTask {
             });
         }
 
-        layout_root.destroy(self.flow_leaf_set.get());
+        layout_root.destroy();
 
         // Tell script that we're done.
         //
@@ -700,7 +693,7 @@ impl LayoutTask {
             // The neat thing here is that in order to answer the following two queries we only
             // need to compare nodes for equality. Thus we can safely work only with `OpaqueNode`.
             ContentBoxQuery(node, reply_chan) => {
-                let node = OpaqueNode::from_script_node(&node);
+                let node = OpaqueNode::from_script_node(node);
 
                 fn union_boxes_for_node<'a>(
                                         accumulator: &mut Option<Rect<Au>>,
@@ -724,7 +717,7 @@ impl LayoutTask {
                 reply_chan.send(ContentBoxResponse(rect.unwrap_or(Au::zero_rect())))
             }
             ContentBoxesQuery(node, reply_chan) => {
-                let node = OpaqueNode::from_script_node(&node);
+                let node = OpaqueNode::from_script_node(node);
 
                 fn add_boxes_for_node<'a>(
                                       accumulator: &mut ~[Rect<Au>],
diff --git a/src/components/main/layout/parallel.rs b/src/components/main/layout/parallel.rs
index f6ddc27cce4..5e4da051dbc 100644
--- a/src/components/main/layout/parallel.rs
+++ b/src/components/main/layout/parallel.rs
@@ -7,15 +7,17 @@
 //! This code is highly unsafe. Keep this file small and easy to audit.
 
 use css::matching::{ApplicableDeclarations, CannotShare, MatchMethods, StyleWasShared};
+use layout::construct::FlowConstructor;
 use layout::context::LayoutContext;
 use layout::extra::LayoutAuxMethods;
-use layout::flow::{Flow, FlowLeafSet, PostorderFlowTraversal};
+use layout::flow::{Flow, PreorderFlowTraversal, PostorderFlowTraversal};
 use layout::flow;
-use layout::layout_task::{AssignHeightsAndStoreOverflowTraversal, BubbleWidthsTraversal};
+use layout::layout_task::{AssignHeightsAndStoreOverflowTraversal, AssignWidthsTraversal};
+use layout::layout_task::{BubbleWidthsTraversal};
 use layout::util::{LayoutDataAccess, OpaqueNode};
-use layout::wrapper::{layout_node_to_unsafe_layout_node, LayoutNode, UnsafeLayoutNode};
+use layout::wrapper::{layout_node_to_unsafe_layout_node, LayoutNode, PostorderNodeMutTraversal};
+use layout::wrapper::{ThreadSafeLayoutNode, UnsafeLayoutNode};
 
-use extra::arc::Arc;
 use servo_util::time::{ProfilerChan, profile};
 use servo_util::time;
 use servo_util::workqueue::{WorkQueue, WorkUnit, WorkerProxy};
@@ -24,11 +26,36 @@ use std::ptr;
 use std::sync::atomics::{AtomicInt, Relaxed, SeqCst};
 use style::{Stylist, TNode};
 
-pub enum TraversalKind {
-    BubbleWidthsTraversalKind,
-    AssignHeightsAndStoreOverflowTraversalKind,
+#[allow(dead_code)]
+fn static_assertion(node: UnsafeLayoutNode) {
+    unsafe {
+        let _: PaddedUnsafeFlow = ::std::unstable::intrinsics::transmute(node);
+    }
+}
+
+/// Memory representation that is at least as large as UnsafeLayoutNode, as it must be
+/// safely transmutable to and from that type to accommodate the type-unsafe parallel work
+/// queue usage that stores both flows and nodes.
+pub type PaddedUnsafeFlow = (uint, uint, uint);
+
+trait UnsafeFlowConversions {
+    fn to_flow(&self) -> UnsafeFlow;
+    fn from_flow(flow: &UnsafeFlow) -> Self;
+}
+
+impl UnsafeFlowConversions for PaddedUnsafeFlow {
+    fn to_flow(&self) -> UnsafeFlow {
+        let (vtable, ptr, _padding) = *self;
+        (vtable, ptr)
+    }
+
+    fn from_flow(flow: &UnsafeFlow) -> PaddedUnsafeFlow {
+        let &(vtable, ptr) = flow;
+        (vtable, ptr, 0)
+    }
 }
 
+/// Vtable + pointer representation of a Flow trait object.
 pub type UnsafeFlow = (uint, uint);
 
 fn null_unsafe_flow() -> UnsafeFlow {
@@ -92,7 +119,9 @@ impl FlowParallelInfo {
 
 /// A parallel bottom-up flow traversal.
 trait ParallelPostorderFlowTraversal : PostorderFlowTraversal {
-    fn run_parallel(&mut self, mut unsafe_flow: UnsafeFlow) {
+    fn run_parallel(&mut self,
+                    mut unsafe_flow: UnsafeFlow,
+                    _: &mut WorkerProxy<*mut LayoutContext,PaddedUnsafeFlow>) {
         loop {
             unsafe {
                 // Get a real flow.
@@ -131,17 +160,69 @@ trait ParallelPostorderFlowTraversal : PostorderFlowTraversal {
     }
 }
 
+/// A parallel top-down flow traversal.
+trait ParallelPreorderFlowTraversal : PreorderFlowTraversal {
+    fn run_parallel(&mut self,
+                    unsafe_flow: UnsafeFlow,
+                    proxy: &mut WorkerProxy<*mut LayoutContext,PaddedUnsafeFlow>);
+
+    fn run_parallel_helper(&mut self,
+                           unsafe_flow: UnsafeFlow,
+                           proxy: &mut WorkerProxy<*mut LayoutContext,PaddedUnsafeFlow>,
+                           top_down_func: extern "Rust" fn(PaddedUnsafeFlow,
+                                                           &mut WorkerProxy<*mut LayoutContext,
+                                                                            PaddedUnsafeFlow>),
+                           bottom_up_func: extern "Rust" fn(PaddedUnsafeFlow,
+                                                            &mut WorkerProxy<*mut LayoutContext,
+                                                                             PaddedUnsafeFlow>)) {
+        let mut had_children = false;
+        unsafe {
+            // Get a real flow.
+            let flow: &mut ~Flow = cast::transmute(&unsafe_flow);
+
+            // Perform the appropriate traversal.
+            self.process(*flow);
+
+            // Possibly enqueue the children.
+            for kid in flow::child_iter(*flow) {
+                had_children = true;
+                proxy.push(WorkUnit {
+                    fun: top_down_func,
+                    data: UnsafeFlowConversions::from_flow(&borrowed_flow_to_unsafe_flow(kid)),
+                });
+            }
+
+        }
+
+        // If there were no more children, start assigning heights.
+        if !had_children {
+            bottom_up_func(UnsafeFlowConversions::from_flow(&unsafe_flow), proxy)
+        }
+    }
+}
+
 impl<'a> ParallelPostorderFlowTraversal for BubbleWidthsTraversal<'a> {}
 
+impl<'a> ParallelPreorderFlowTraversal for AssignWidthsTraversal<'a> {
+    fn run_parallel(&mut self,
+                    unsafe_flow: UnsafeFlow,
+                    proxy: &mut WorkerProxy<*mut LayoutContext,PaddedUnsafeFlow>) {
+        self.run_parallel_helper(unsafe_flow,
+                                 proxy,
+                                 assign_widths,
+                                 assign_heights_and_store_overflow)
+    }
+}
+
 impl<'a> ParallelPostorderFlowTraversal for AssignHeightsAndStoreOverflowTraversal<'a> {}
 
-fn match_and_cascade_node(unsafe_layout_node: UnsafeLayoutNode,
-                          proxy: &mut WorkerProxy<*mut LayoutContext,UnsafeLayoutNode>) {
+fn recalc_style_for_node(unsafe_layout_node: UnsafeLayoutNode,
+                         proxy: &mut WorkerProxy<*mut LayoutContext,UnsafeLayoutNode>) {
     unsafe {
         let layout_context: &mut LayoutContext = cast::transmute(*proxy.user_data());
 
         // Get a real layout node.
-        let node: LayoutNode = cast::transmute(unsafe_layout_node);
+        let node: LayoutNode = ::std::unstable::intrinsics::transmute(unsafe_layout_node);
 
         // Initialize layout data.
         //
@@ -159,7 +240,7 @@ fn match_and_cascade_node(unsafe_layout_node: UnsafeLayoutNode,
         // First, check to see whether we can share a style with someone.
         let style_sharing_candidate_cache = layout_context.style_sharing_candidate_cache();
         let sharing_result = node.share_style_if_possible(style_sharing_candidate_cache,
-                                                          parent_opt);
+                                                          parent_opt.clone());
 
         // Otherwise, match and cascade selectors.
         match sharing_result {
@@ -186,24 +267,61 @@ fn match_and_cascade_node(unsafe_layout_node: UnsafeLayoutNode,
             StyleWasShared(index) => style_sharing_candidate_cache.touch(index),
         }
 
-        // Enqueue kids.
+        // Prepare for flow construction by counting the node's children and storing that count.
         let mut child_count = 0;
-        for kid in node.children() {
+        for _ in node.children() {
             child_count += 1;
+        }
+        if child_count != 0 {
+            let mut layout_data_ref = node.mutate_layout_data();
+            match *layout_data_ref.get() {
+                Some(ref mut layout_data) => {
+                    layout_data.data.parallel.children_count.store(child_count as int, Relaxed)
+                }
+                None => fail!("no layout data"),
+            }
 
-            proxy.push(WorkUnit {
-                fun: match_and_cascade_node,
-                data: layout_node_to_unsafe_layout_node(&kid),
-            });
+            // Enqueue kids.
+            for kid in node.children() {
+                proxy.push(WorkUnit {
+                    fun: recalc_style_for_node,
+                    data: layout_node_to_unsafe_layout_node(&kid),
+                });
+            }
+            return
         }
 
-        // Prepare for flow construction by adding this node to the leaf set or counting its
-        // children.
-        if child_count == 0 {
-            // We don't need set the `child_count` field here since that's only used by kids during
-            // bottom-up traversals, and since this node is a leaf it has no kids.
-            layout_context.dom_leaf_set.get().insert(&node);
-        } else {
+        // If we got here, we're a leaf. Start construction of flows for this node.
+        construct_flows(unsafe_layout_node, proxy)
+    }
+}
+
+fn construct_flows(mut unsafe_layout_node: UnsafeLayoutNode,
+                   proxy: &mut WorkerProxy<*mut LayoutContext,UnsafeLayoutNode>) {
+    loop {
+        let layout_context: &mut LayoutContext = unsafe {
+            cast::transmute(*proxy.user_data())
+        };
+
+        // Get a real layout node.
+        let node: LayoutNode = unsafe {
+            cast::transmute(unsafe_layout_node)
+        };
+
+        // Construct flows for this node.
+        {
+            let mut flow_constructor = FlowConstructor::new(layout_context, None);
+            flow_constructor.process(&ThreadSafeLayoutNode::new(&node));
+        }
+
+        // Reset the count of children for the next traversal.
+        //
+        // FIXME(pcwalton): Use children().len() when the implementation of that is efficient.
+        let mut child_count = 0;
+        for _ in node.children() {
+            child_count += 1
+        }
+        {
             let mut layout_data_ref = node.mutate_layout_data();
             match *layout_data_ref.get() {
                 Some(ref mut layout_data) => {
@@ -212,40 +330,75 @@ fn match_and_cascade_node(unsafe_layout_node: UnsafeLayoutNode,
                 None => fail!("no layout data"),
             }
         }
+
+        // If this is the reflow root, we're done.
+        if layout_context.reflow_root == OpaqueNode::from_layout_node(&node) {
+            break
+        }
+
+        // Otherwise, enqueue the parent.
+        match node.parent_node() {
+            Some(parent) => {
+
+                // No, we're not at the root yet. Then are we the last sibling of our parent?
+                // If so, we can continue on with our parent; otherwise, we've gotta wait.
+                unsafe {
+                    match *parent.borrow_layout_data_unchecked() {
+                        Some(ref parent_layout_data) => {
+                            let parent_layout_data = cast::transmute_mut(parent_layout_data);
+                            if parent_layout_data.data
+                                                 .parallel
+                                                 .children_count
+                                                 .fetch_sub(1, SeqCst) == 1 {
+                                // We were the last child of our parent. Construct flows for our
+                                // parent.
+                                unsafe_layout_node = layout_node_to_unsafe_layout_node(&parent)
+                            } else {
+                                // Get out of here and find another node to work on.
+                                break
+                            }
+                        }
+                        None => fail!("no layout data for parent?!"),
+                    }
+                }
+            }
+            None => fail!("no parent and weren't at reflow root?!"),
+        }
     }
 }
 
-fn bubble_widths(unsafe_flow: UnsafeFlow, proxy: &mut WorkerProxy<*mut LayoutContext,UnsafeFlow>) {
+fn assign_widths(unsafe_flow: PaddedUnsafeFlow,
+                 proxy: &mut WorkerProxy<*mut LayoutContext,PaddedUnsafeFlow>) {
     let layout_context: &mut LayoutContext = unsafe {
         cast::transmute(*proxy.user_data())
     };
-    let mut bubble_widths_traversal = BubbleWidthsTraversal {
+    let mut assign_widths_traversal = AssignWidthsTraversal {
         layout_context: layout_context,
     };
-    bubble_widths_traversal.run_parallel(unsafe_flow)
+    assign_widths_traversal.run_parallel(unsafe_flow.to_flow(), proxy)
 }
 
-fn assign_heights_and_store_overflow(unsafe_flow: UnsafeFlow,
-                                     proxy: &mut WorkerProxy<*mut LayoutContext,UnsafeFlow>) {
+fn assign_heights_and_store_overflow(unsafe_flow: PaddedUnsafeFlow,
+                                     proxy: &mut WorkerProxy<*mut LayoutContext,PaddedUnsafeFlow>) {
     let layout_context: &mut LayoutContext = unsafe {
         cast::transmute(*proxy.user_data())
     };
     let mut assign_heights_traversal = AssignHeightsAndStoreOverflowTraversal {
         layout_context: layout_context,
     };
-    assign_heights_traversal.run_parallel(unsafe_flow)
+    assign_heights_traversal.run_parallel(unsafe_flow.to_flow(), proxy)
 }
 
-pub fn match_and_cascade_subtree(root_node: &LayoutNode,
-                                 layout_context: &mut LayoutContext,
-                                 queue: &mut WorkQueue<*mut LayoutContext,UnsafeLayoutNode>) {
+pub fn recalc_style_for_subtree(root_node: &LayoutNode,
+                                layout_context: &mut LayoutContext,
+                                queue: &mut WorkQueue<*mut LayoutContext,UnsafeLayoutNode>) {
     unsafe {
         queue.data = cast::transmute(layout_context)
     }
 
     // Enqueue the root node.
     queue.push(WorkUnit {
-        fun: match_and_cascade_node,
+        fun: recalc_style_for_node,
         data: layout_node_to_unsafe_layout_node(root_node),
     });
 
@@ -254,27 +407,19 @@ pub fn match_and_cascade_subtree(root_node: &LayoutNode,
     queue.data = ptr::mut_null()
 }
 
-pub fn traverse_flow_tree(kind: TraversalKind,
-                          leaf_set: &Arc<FlowLeafSet>,
-                          profiler_chan: ProfilerChan,
-                          layout_context: &mut LayoutContext,
-                          queue: &mut WorkQueue<*mut LayoutContext,UnsafeFlow>) {
+pub fn traverse_flow_tree_preorder(root: &mut ~Flow,
+                                   profiler_chan: ProfilerChan,
+                                   layout_context: &mut LayoutContext,
+                                   queue: &mut WorkQueue<*mut LayoutContext,PaddedUnsafeFlow>) {
     unsafe {
         queue.data = cast::transmute(layout_context)
     }
 
-    let fun = match kind {
-        BubbleWidthsTraversalKind => bubble_widths,
-        AssignHeightsAndStoreOverflowTraversalKind => assign_heights_and_store_overflow,
-    };
-
     profile(time::LayoutParallelWarmupCategory, profiler_chan, || {
-        for (flow, _) in leaf_set.get().iter() {
-            queue.push(WorkUnit {
-                fun: fun,
-                data: *flow,
-            })
-        }
+        queue.push(WorkUnit {
+            fun: assign_widths,
+            data: UnsafeFlowConversions::from_flow(&mut_owned_flow_to_unsafe_flow(root)),
+        })
     });
 
     queue.run();
diff --git a/src/components/main/layout/util.rs b/src/components/main/layout/util.rs
index 7a2eeb8f805..de10f8a8d9a 100644
--- a/src/components/main/layout/util.rs
+++ b/src/components/main/layout/util.rs
@@ -8,9 +8,10 @@ use layout::parallel::DomParallelInfo;
 use layout::wrapper::{LayoutNode, TLayoutNode, ThreadSafeLayoutNode};
 
 use extra::arc::Arc;
+use script::dom::bindings::js::JS;
 use script::dom::bindings::utils::Reflectable;
-use script::dom::node::AbstractNode;
-use script::layout_interface::{LayoutChan, UntrustedNodeAddress};
+use script::dom::node::Node;
+use script::layout_interface::{LayoutChan, UntrustedNodeAddress, TrustedNodeAddress};
 use servo_util::range::Range;
 use std::cast;
 use std::cell::{Ref, RefMut};
@@ -212,23 +213,28 @@ impl OpaqueNode {
     /// Converts a DOM node (layout view) to an `OpaqueNode`.
     pub fn from_layout_node(node: &LayoutNode) -> OpaqueNode {
         unsafe {
-            let abstract_node = node.get_abstract();
-            let ptr: uintptr_t = cast::transmute(abstract_node.reflector().get_jsobject());
-            OpaqueNode(ptr)
+            OpaqueNode::from_jsmanaged(node.get_jsmanaged())
         }
     }
 
     /// Converts a thread-safe DOM node (layout view) to an `OpaqueNode`.
     pub fn from_thread_safe_layout_node(node: &ThreadSafeLayoutNode) -> OpaqueNode {
         unsafe {
-            let abstract_node = node.get_abstract();
+            let abstract_node = node.get_jsmanaged();
             let ptr: uintptr_t = cast::transmute(abstract_node.reflector().get_jsobject());
             OpaqueNode(ptr)
         }
     }
 
     /// Converts a DOM node (script view) to an `OpaqueNode`.
-    pub fn from_script_node(node: &AbstractNode) -> OpaqueNode {
+    pub fn from_script_node(node: TrustedNodeAddress) -> OpaqueNode {
+        unsafe {
+            OpaqueNode::from_jsmanaged(&JS::from_trusted_node_address(node))
+        }
+    }
+
+    /// Converts a DOM node to an `OpaqueNode'.
+    fn from_jsmanaged(node: &JS<Node>) -> OpaqueNode {
         unsafe {
             let ptr: uintptr_t = cast::transmute(node.reflector().get_jsobject());
             OpaqueNode(ptr)
diff --git a/src/components/main/layout/wrapper.rs b/src/components/main/layout/wrapper.rs
index 2e67eff3567..a5830b7f00c 100644
--- a/src/components/main/layout/wrapper.rs
+++ b/src/components/main/layout/wrapper.rs
@@ -11,18 +11,20 @@
 //!
 //! (1) Layout is not allowed to mutate the DOM.
 //!
-//! (2) Layout is not allowed to see anything with `Abstract` in the name, because it could hang
+//! (2) Layout is not allowed to see anything with `JS` in the name, because it could hang
 //!     onto these objects and cause use-after-free.
 
 use extra::url::Url;
+use script::dom::bindings::codegen::InheritTypes::{HTMLImageElementCast, HTMLIFrameElementCast};
+use script::dom::bindings::codegen::InheritTypes::{TextCast, ElementCast};
+use script::dom::bindings::js::JS;
 use script::dom::element::{Element, HTMLAreaElementTypeId, HTMLAnchorElementTypeId};
 use script::dom::element::{HTMLLinkElementTypeId};
 use script::dom::htmliframeelement::HTMLIFrameElement;
 use script::dom::htmlimageelement::HTMLImageElement;
-use script::dom::node::{AbstractNode, DocumentNodeTypeId, ElementNodeTypeId, Node, NodeTypeId};
+use script::dom::node::{DocumentNodeTypeId, ElementNodeTypeId, Node, NodeTypeId, NodeHelpers};
 use script::dom::text::Text;
 use servo_msg::constellation_msg::{PipelineId, SubpageId};
-use servo_util::concurrentmap::{ConcurrentHashMap, ConcurrentHashMapIterator};
 use servo_util::namespace;
 use servo_util::namespace::Namespace;
 use std::cast;
@@ -35,20 +37,20 @@ use layout::util::LayoutDataWrapper;
 /// Allows some convenience methods on generic layout nodes.
 pub trait TLayoutNode {
     /// Creates a new layout node with the same lifetime as this layout node.
-    unsafe fn new_with_this_lifetime(&self, node: AbstractNode) -> Self;
+    unsafe fn new_with_this_lifetime(&self, node: JS<Node>) -> Self;
 
     /// Returns the type ID of this node. Fails if this node is borrowed mutably.
     fn type_id(&self) -> NodeTypeId;
 
-    /// Returns the interior of this node as an `AbstractNode`. This is highly unsafe for layout to
+
+    /// Returns the interior of this node as a `JS`. This is highly unsafe for layout to
     /// call and as such is marked `unsafe`.
-    unsafe fn get_abstract(&self) -> AbstractNode;
+    unsafe fn get_jsmanaged<'a>(&'a self) -> &'a JS<Node>;
 
     /// Returns the interior of this node as a `Node`. This is highly unsafe for layout to call
     /// and as such is marked `unsafe`.
     unsafe fn get<'a>(&'a self) -> &'a Node {
-        let node = self.get_abstract();
-        cast::transmute(node.node())
+        self.get_jsmanaged().get()
     }
 
     fn node_is_element(&self) -> bool {
@@ -70,40 +72,18 @@ pub trait TLayoutNode {
     /// FIXME(pcwalton): Don't copy URLs.
     fn image_url(&self) -> Option<Url> {
         unsafe {
-            self.with_image_element(|image_element| {
-                image_element.image.as_ref().map(|url| (*url).clone())
-            })
-        }
-    }
-
-    /// Downcasts this node to an iframe element and calls the given closure.
-    ///
-    /// FIXME(pcwalton): RAII.
-    unsafe fn with_iframe_element<R>(&self, f: |&HTMLIFrameElement| -> R) -> R {
-        if !self.get_abstract().is_iframe_element() {
-            fail!(~"node is not an iframe element");
+            let image_element: JS<HTMLImageElement> = HTMLImageElementCast::to(self.get_jsmanaged());
+            image_element.get().extra.image.as_ref().map(|url| (*url).clone())
         }
-        self.get_abstract().transmute(f)
-    }
-
-    /// Downcasts this node to an image element and calls the given closure.
-    ///
-    /// FIXME(pcwalton): RAII.
-    unsafe fn with_image_element<R>(&self, f: |&HTMLImageElement| -> R) -> R {
-        if !self.get_abstract().is_image_element() {
-            fail!(~"node is not an image element");
-        }
-        self.get_abstract().transmute(f)
     }
 
     /// If this node is an iframe element, returns its pipeline and subpage IDs. If this node is
     /// not an iframe element, fails.
     fn iframe_pipeline_and_subpage_ids(&self) -> (PipelineId, SubpageId) {
         unsafe {
-            self.with_iframe_element(|iframe_element| {
-                let size = iframe_element.size.unwrap();
-                (size.pipeline_id, size.subpage_id)
-            })
+            let iframe_element: JS<HTMLIFrameElement> = HTMLIFrameElementCast::to(self.get_jsmanaged());
+            let size = iframe_element.get().size.unwrap();
+            (size.pipeline_id, size.subpage_id)
         }
     }
 
@@ -112,45 +92,39 @@ pub trait TLayoutNode {
     /// FIXME(pcwalton): Don't copy text. Atomically reference count instead.
     fn text(&self) -> ~str {
         unsafe {
-            self.with_text(|text| text.characterdata.data.to_str())
+            let text: JS<Text> = TextCast::to(self.get_jsmanaged());
+            text.get().characterdata.data.to_str()
         }
     }
 
-    /// Downcasts this node to a text node and calls the given closure.
-    ///
-    /// FIXME(pcwalton): RAII.
-    unsafe fn with_text<R>(&self, f: |&Text| -> R) -> R {
-        self.get_abstract().with_imm_text(f)
-    }
-
     /// Returns the first child of this node.
     fn first_child(&self) -> Option<Self> {
         unsafe {
-            self.get_abstract().first_child().map(|node| self.new_with_this_lifetime(node))
+            self.get_jsmanaged().first_child().map(|node| self.new_with_this_lifetime(node))
         }
     }
 
     /// Dumps this node tree, for debugging.
     fn dump(&self) {
         unsafe {
-            self.get_abstract().dump()
+            self.get_jsmanaged().dump()
         }
     }
 }
 
 /// A wrapper so that layout can access only the methods that it should have access to. Layout must
-/// only ever see these and must never see instances of `AbstractNode`.
+/// only ever see these and must never see instances of `JS`.
 #[deriving(Clone, Eq)]
 pub struct LayoutNode<'a> {
     /// The wrapped node.
-    priv node: AbstractNode,
+    priv node: JS<Node>,
 
     /// Being chained to a value prevents `LayoutNode`s from escaping.
     priv chain: &'a (),
 }
 
 impl<'ln> TLayoutNode for LayoutNode<'ln> {
-    unsafe fn new_with_this_lifetime(&self, node: AbstractNode) -> LayoutNode<'ln> {
+    unsafe fn new_with_this_lifetime(&self, node: JS<Node>) -> LayoutNode<'ln> {
         LayoutNode {
             node: node,
             chain: self.chain,
@@ -159,14 +133,14 @@ impl<'ln> TLayoutNode for LayoutNode<'ln> {
     fn type_id(&self) -> NodeTypeId {
         self.node.type_id()
     }
-    unsafe fn get_abstract(&self) -> AbstractNode {
-        self.node
+    unsafe fn get_jsmanaged<'a>(&'a self) -> &'a JS<Node> {
+        &self.node
     }
 }
 
 impl<'ln> LayoutNode<'ln> {
     /// Creates a new layout node, scoped to the given closure.
-    pub unsafe fn with_layout_node<R>(node: AbstractNode, f: <'a> |LayoutNode<'a>| -> R) -> R {
+    pub unsafe fn with_layout_node<R>(node: JS<Node>, f: <'a> |LayoutNode<'a>| -> R) -> R {
         let heavy_iron_ball = ();
         f(LayoutNode {
             node: node,
@@ -194,34 +168,34 @@ impl<'ln> LayoutNode<'ln> {
 impl<'ln> TNode<LayoutElement<'ln>> for LayoutNode<'ln> {
     fn parent_node(&self) -> Option<LayoutNode<'ln>> {
         unsafe {
-            self.node.node().parent_node.map(|node| self.new_with_this_lifetime(node))
+            self.node.parent_node().map(|node| self.new_with_this_lifetime(node))
         }
     }
 
     fn prev_sibling(&self) -> Option<LayoutNode<'ln>> {
         unsafe {
-            self.node.node().prev_sibling.map(|node| self.new_with_this_lifetime(node))
+            self.node.prev_sibling().map(|node| self.new_with_this_lifetime(node))
         }
     }
 
     fn next_sibling(&self) -> Option<LayoutNode<'ln>> {
         unsafe {
-            self.node.node().next_sibling.map(|node| self.new_with_this_lifetime(node))
+            self.node.next_sibling().map(|node| self.new_with_this_lifetime(node))
         }
     }
 
     /// If this is an element, accesses the element data. Fails if this is not an element node.
     #[inline]
     fn with_element<R>(&self, f: |&LayoutElement<'ln>| -> R) -> R {
-        self.node.with_imm_element(|element| {
-            // FIXME(pcwalton): Workaround until Rust gets multiple lifetime parameters on
-            // implementations.
-            unsafe {
-                f(&LayoutElement {
-                    element: cast::transmute_region(element),
-                })
-            }
-        })
+        let elem: JS<Element> = ElementCast::to(&self.node);
+        let element = elem.get();
+        // FIXME(pcwalton): Workaround until Rust gets multiple lifetime parameters on
+        // implementations.
+        unsafe {
+            f(&LayoutElement {
+                element: cast::transmute_region(element),
+            })
+        }
     }
 
     fn is_element(&self) -> bool {
@@ -257,8 +231,8 @@ pub struct LayoutNodeChildrenIterator<'a> {
 
 impl<'a> Iterator<LayoutNode<'a>> for LayoutNodeChildrenIterator<'a> {
     fn next(&mut self) -> Option<LayoutNode<'a>> {
-        let node = self.current_node;
-        self.current_node = self.current_node.and_then(|node| {
+        let node = self.current_node.clone();
+        self.current_node = node.clone().and_then(|node| {
             node.next_sibling()
         });
         node
@@ -358,7 +332,7 @@ impl<'le> TElement for LayoutElement<'le> {
 /// node does not allow any parents or siblings of nodes to be accessed, to avoid races.
 pub struct ThreadSafeLayoutNode<'ln> {
     /// The wrapped node.
-    priv node: AbstractNode,
+    priv node: JS<Node>,
 
     /// Being chained to a value prevents `ThreadSafeLayoutNode`s from escaping.
     priv chain: &'ln (),
@@ -366,7 +340,7 @@ pub struct ThreadSafeLayoutNode<'ln> {
 
 impl<'ln> TLayoutNode for ThreadSafeLayoutNode<'ln> {
     /// Creates a new layout node with the same lifetime as this layout node.
-    unsafe fn new_with_this_lifetime(&self, node: AbstractNode) -> ThreadSafeLayoutNode<'ln> {
+    unsafe fn new_with_this_lifetime(&self, node: JS<Node>) -> ThreadSafeLayoutNode<'ln> {
         ThreadSafeLayoutNode {
             node: node,
             chain: self.chain,
@@ -375,23 +349,32 @@ impl<'ln> TLayoutNode for ThreadSafeLayoutNode<'ln> {
     fn type_id(&self) -> NodeTypeId {
         self.node.type_id()
     }
-    unsafe fn get_abstract(&self) -> AbstractNode {
-        self.node
+    unsafe fn get_jsmanaged<'a>(&'a self) -> &'a JS<Node> {
+        &self.node
+    }
+}
+
+impl<'ln> Clone for ThreadSafeLayoutNode<'ln> {
+    fn clone(&self) -> ThreadSafeLayoutNode<'ln> {
+        ThreadSafeLayoutNode {
+            node: self.node.clone(),
+            chain: self.chain,
+        }
     }
 }
 
 impl<'ln> ThreadSafeLayoutNode<'ln> {
     /// Creates a new `ThreadSafeLayoutNode` from the given `LayoutNode`.
-    pub fn new<'a>(node: LayoutNode<'a>) -> ThreadSafeLayoutNode<'a> {
+    pub fn new<'a>(node: &LayoutNode<'a>) -> ThreadSafeLayoutNode<'a> {
         ThreadSafeLayoutNode {
-            node: node.node,
+            node: node.node.clone(),
             chain: node.chain,
         }
     }
 
     /// Returns the next sibling of this node. Unsafe and private because this can lead to races.
     unsafe fn next_sibling(&self) -> Option<ThreadSafeLayoutNode<'ln>> {
-        self.node.node().next_sibling.map(|node| self.new_with_this_lifetime(node))
+        self.node.next_sibling().map(|node| self.new_with_this_lifetime(node))
     }
 
     /// Returns an iterator over this node's children.
@@ -405,12 +388,12 @@ impl<'ln> ThreadSafeLayoutNode<'ln> {
     #[inline]
     pub fn with_element<R>(&self, f: |&ThreadSafeLayoutElement| -> R) -> R {
         unsafe {
-            self.get_abstract().with_imm_element(|element| {
-                // FIXME(pcwalton): Workaround until Rust gets multiple lifetime parameters on
-                // implementations.
-                f(&ThreadSafeLayoutElement {
-                    element: cast::transmute_region(element),
-                })
+            let elem: JS<Element> = ElementCast::to(&self.node);
+            let element = elem.get();
+            // FIXME(pcwalton): Workaround until Rust gets multiple lifetime parameters on
+            // implementations.
+            f(&ThreadSafeLayoutElement {
+                element: cast::transmute_region(element),
             })
         }
     }
@@ -434,7 +417,7 @@ impl<'ln> ThreadSafeLayoutNode<'ln> {
     /// Traverses the tree in postorder.
     ///
     /// TODO(pcwalton): Offer a parallel version with a compatible API.
-    pub fn traverse_postorder_mut<T:PostorderNodeMutTraversal>(mut self, traversal: &mut T)
+    pub fn traverse_postorder_mut<T:PostorderNodeMutTraversal>(&mut self, traversal: &mut T)
                                   -> bool {
         if traversal.should_prune(self) {
             return true
@@ -444,7 +427,7 @@ impl<'ln> ThreadSafeLayoutNode<'ln> {
         loop {
             match opt_kid {
                 None => break,
-                Some(kid) => {
+                Some(mut kid) => {
                     if !kid.traverse_postorder_mut(traversal) {
                         return false
                     }
@@ -465,8 +448,8 @@ pub struct ThreadSafeLayoutNodeChildrenIterator<'a> {
 
 impl<'a> Iterator<ThreadSafeLayoutNode<'a>> for ThreadSafeLayoutNodeChildrenIterator<'a> {
     fn next(&mut self) -> Option<ThreadSafeLayoutNode<'a>> {
-        let node = self.current_node;
-        self.current_node = self.current_node.and_then(|node| {
+        let node = self.current_node.clone();
+        self.current_node = self.current_node.clone().and_then(|node| {
             unsafe {
                 node.next_sibling()
             }
@@ -491,17 +474,19 @@ impl<'le> ThreadSafeLayoutElement<'le> {
 /// A bottom-up, parallelizable traversal.
 pub trait PostorderNodeMutTraversal {
     /// The operation to perform. Return true to continue or false to stop.
-    fn process<'a>(&'a mut self, node: ThreadSafeLayoutNode<'a>) -> bool;
+    fn process<'a>(&'a mut self, node: &ThreadSafeLayoutNode<'a>) -> bool;
 
     /// Returns true if this node should be pruned. If this returns true, we skip the operation
     /// entirely and do not process any descendant nodes. This is called *before* child nodes are
     /// visited. The default implementation never prunes any nodes.
-    fn should_prune<'a>(&'a self, _node: ThreadSafeLayoutNode<'a>) -> bool {
+    fn should_prune<'a>(&'a self, _node: &ThreadSafeLayoutNode<'a>) -> bool {
         false
     }
 }
 
-pub type UnsafeLayoutNode = (uint, uint);
+/// Opaque type stored in type-unsafe work queues for parallel layout.
+/// Must be transmutable to and from LayoutNode/ThreadsafeLayoutNode/PaddedUnsafeFlow.
+pub type UnsafeLayoutNode = (uint, uint, uint);
 
 pub fn layout_node_to_unsafe_layout_node(node: &LayoutNode) -> UnsafeLayoutNode {
     unsafe {
@@ -509,32 +494,3 @@ pub fn layout_node_to_unsafe_layout_node(node: &LayoutNode) -> UnsafeLayoutNode
     }
 }
 
-/// Keeps track of the leaves of the DOM. This is used to efficiently start bottom-up traversals.
-pub struct DomLeafSet {
-    priv set: ConcurrentHashMap<UnsafeLayoutNode,()>,
-}
-
-impl DomLeafSet {
-    /// Creates a new DOM leaf set.
-    pub fn new() -> DomLeafSet {
-        DomLeafSet {
-            set: ConcurrentHashMap::with_locks_and_buckets(64, 256),
-        }
-    }
-
-    /// Inserts a DOM node into the leaf set.
-    pub fn insert(&self, node: &LayoutNode) {
-        self.set.insert(layout_node_to_unsafe_layout_node(node), ());
-    }
-
-    /// Removes all DOM nodes from the set.
-    pub fn clear(&self) {
-        self.set.clear()
-    }
-
-    /// Iterates over the DOM nodes in the leaf set.
-    pub fn iter<'a>(&'a self) -> ConcurrentHashMapIterator<'a,UnsafeLayoutNode,()> {
-        self.set.iter()
-    }
-}
-
diff --git a/src/components/main/pipeline.rs b/src/components/main/pipeline.rs
index 3017e9653c5..68b64d66c48 100644
--- a/src/components/main/pipeline.rs
+++ b/src/components/main/pipeline.rs
@@ -7,7 +7,6 @@ use layout::layout_task::LayoutTask;
 
 use extra::url::Url;
 use geom::size::Size2D;
-use gfx::opts::Opts;
 use gfx::render_task::{PaintPermissionGranted, PaintPermissionRevoked};
 use gfx::render_task::{RenderChan, RenderTask};
 use layout::util::OpaqueNode;
@@ -18,6 +17,7 @@ use script::script_task;
 use servo_msg::constellation_msg::{ConstellationChan, Failure, PipelineId, SubpageId};
 use servo_net::image_cache_task::ImageCacheTask;
 use servo_net::resource_task::ResourceTask;
+use servo_util::opts::Opts;
 use servo_util::time::ProfilerChan;
 use std::cell::RefCell;
 //FIXME: switch to std::rc when we upgrade Rust
diff --git a/src/components/main/servo.rs b/src/components/main/servo.rs
index b21c292255b..53071519273 100755
--- a/src/components/main/servo.rs
+++ b/src/components/main/servo.rs
@@ -47,18 +47,16 @@ use constellation::Constellation;
 use servo_msg::constellation_msg::InitLoadUrlMsg;
 
 #[cfg(not(test))]
-use gfx::opts;
-
-#[cfg(not(test))]
 use servo_net::image_cache_task::{ImageCacheTask, SyncImageCacheTask};
 #[cfg(not(test))]
 use servo_net::resource_task::ResourceTask;
 #[cfg(not(test))]
 use servo_util::time::Profiler;
 
-pub use gfx::opts::Opts;
-pub use gfx::text;
-pub use servo_util::url::parse_url;
+#[cfg(not(test))]
+use servo_util::opts;
+#[cfg(not(test))]
+use servo_util::url::parse_url;
 
 #[cfg(not(test))]
 use std::os;
@@ -138,7 +136,7 @@ pub extern "C" fn android_start(argc: int, argv: **u8) -> int {
 }
 
 #[cfg(not(test))]
-fn run(opts: Opts) {
+fn run(opts: opts::Opts) {
     let mut pool = green::SchedPool::new(green::PoolConfig::new());
 
     let (compositor_port, compositor_chan) = CompositorChan::new();
diff --git a/src/components/msg/compositor_msg.rs b/src/components/msg/compositor_msg.rs
index c1c28d9b467..4726f20e9a0 100644
--- a/src/components/msg/compositor_msg.rs
+++ b/src/components/msg/compositor_msg.rs
@@ -11,6 +11,8 @@ use layers::platform::surface::{NativeSurface, NativeSurfaceMethods};
 
 use constellation_msg::PipelineId;
 
+use extra::serialize::{Encoder, Encodable};
+
 pub struct LayerBuffer {
     /// The native surface which can be shared between threads or processes. On Mac this is an
     /// `IOSurface`; on Linux this is an X Pixmap; on Android this is an `EGLImageKHR`.
@@ -94,6 +96,11 @@ pub trait ScriptListener : Clone {
     fn close(&self);
 }
 
+impl<S: Encoder> Encodable<S> for @ScriptListener {
+    fn encode(&self, _s: &mut S) {
+    }
+}
+
 /// The interface used by the quadtree and buffer map to get info about layer buffers.
 pub trait Tile {
     /// Returns the amount of memory used by the tile
diff --git a/src/components/msg/constellation_msg.rs b/src/components/msg/constellation_msg.rs
index 9d3c1540066..a2197c26baa 100644
--- a/src/components/msg/constellation_msg.rs
+++ b/src/components/msg/constellation_msg.rs
@@ -60,8 +60,8 @@ pub enum NavigationDirection {
     Back,
 }
 
-#[deriving(Clone, Eq, IterBytes)]
+#[deriving(Clone, Eq, IterBytes, Encodable)]
 pub struct PipelineId(uint);
 
-#[deriving(Clone, Eq, IterBytes)]
+#[deriving(Clone, Eq, IterBytes, Encodable)]
 pub struct SubpageId(uint);
diff --git a/src/components/msg/msg.rs b/src/components/msg/msg.rs
index e27148b09d7..1315979ac18 100644
--- a/src/components/msg/msg.rs
+++ b/src/components/msg/msg.rs
@@ -5,6 +5,8 @@
 #[crate_id = "github.com/mozilla/servo#msg:0.1"];
 #[crate_type = "lib"];
 
+#[feature(managed_boxes)];
+
 extern mod azure;
 extern mod extra;
 extern mod geom;
diff --git a/src/components/net/image_cache_task.rs b/src/components/net/image_cache_task.rs
index fba676cbced..1212fa972c2 100644
--- a/src/components/net/image_cache_task.rs
+++ b/src/components/net/image_cache_task.rs
@@ -14,6 +14,7 @@ use std::util::replace;
 use std::result;
 use extra::arc::{Arc,MutexArc};
 use extra::url::Url;
+use extra::serialize::{Encoder, Encodable};
 
 pub enum Msg {
     /// Tell the cache that we may need a particular image soon. Must be posted
@@ -80,6 +81,11 @@ pub struct ImageCacheTask {
     chan: SharedChan<Msg>,
 }
 
+impl<S: Encoder> Encodable<S> for ImageCacheTask {
+    fn encode(&self, _: &mut S) {
+    }
+}
+
 type DecoderFactory = fn() -> proc(&[u8]) -> Option<Image>;
 
 pub fn ImageCacheTask(resource_task: ResourceTask) -> ImageCacheTask {
diff --git a/src/components/script/dom/attr.rs b/src/components/script/dom/attr.rs
index 6ae8009bb5a..3cf978d69c4 100644
--- a/src/components/script/dom/attr.rs
+++ b/src/components/script/dom/attr.rs
@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::AttrBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::window::Window;
 use servo_util::namespace::{Namespace, Null};
@@ -10,6 +11,7 @@ use servo_util::str::DOMString;
 
 use std::util;
 
+#[deriving(Encodable)]
 pub struct Attr {
     reflector_: Reflector,
     local_name: DOMString,
@@ -43,22 +45,22 @@ impl Attr {
         }
     }
 
-    pub fn new(window: &Window, local_name: DOMString, value: DOMString) -> @mut Attr {
+    pub fn new(window: &Window, local_name: DOMString, value: DOMString) -> JS<Attr> {
         let name = local_name.clone();
         Attr::new_helper(window, local_name, value, name, Null, None)
     }
 
     pub fn new_ns(window: &Window, local_name: DOMString, value: DOMString,
                   name: DOMString, namespace: Namespace,
-                  prefix: Option<DOMString>) -> @mut Attr {
+                  prefix: Option<DOMString>) -> JS<Attr> {
         Attr::new_helper(window, local_name, value, name, namespace, prefix)
     }
 
     fn new_helper(window: &Window, local_name: DOMString, value: DOMString,
                   name: DOMString, namespace: Namespace,
-                  prefix: Option<DOMString>) -> @mut Attr {
+                  prefix: Option<DOMString>) -> JS<Attr> {
         let attr = Attr::new_inherited(local_name, value, name, namespace, prefix);
-        reflect_dom_object(@mut attr, window, AttrBinding::Wrap)
+        reflect_dom_object(~attr, window, AttrBinding::Wrap)
     }
 
     pub fn set_value(&mut self, mut value: DOMString) -> DOMString {
diff --git a/src/components/script/dom/attrlist.rs b/src/components/script/dom/attrlist.rs
index 9b8634de26c..100f057fe8f 100644
--- a/src/components/script/dom/attrlist.rs
+++ b/src/components/script/dom/attrlist.rs
@@ -4,18 +4,20 @@
 
 use dom::attr::Attr;
 use dom::bindings::codegen::AttrListBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
-use dom::node::{AbstractNode};
+use dom::element::Element;
 use dom::window::Window;
 
+#[deriving(Encodable)]
 pub struct AttrList {
     reflector_: Reflector,
-    window: @mut Window,
-    owner: AbstractNode,
+    window: JS<Window>,
+    owner: JS<Element>,
 }
 
 impl AttrList {
-    pub fn new_inherited(window: @mut Window, elem: AbstractNode) -> AttrList {
+    pub fn new_inherited(window: JS<Window>, elem: JS<Element>) -> AttrList {
         AttrList {
             reflector_: Reflector::new(),
             window: window,
@@ -23,22 +25,20 @@ impl AttrList {
         }
     }
 
-    pub fn new(window: @mut Window, elem: AbstractNode) -> @mut AttrList {
-        reflect_dom_object(@mut AttrList::new_inherited(window, elem),
-                           window, AttrListBinding::Wrap)
+    pub fn new(window: &JS<Window>, elem: &JS<Element>) -> JS<AttrList> {
+        reflect_dom_object(~AttrList::new_inherited(window.clone(), elem.clone()),
+                           window.get(), AttrListBinding::Wrap)
     }
 
     pub fn Length(&self) -> u32 {
-        self.owner.with_imm_element(|elem| elem.attrs.len() as u32)
+        self.owner.get().attrs.len() as u32
     }
 
-    pub fn Item(&self, index: u32) -> Option<@mut Attr> {
-        self.owner.with_imm_element(|elem| {
-            elem.attrs.get_opt(index as uint).map(|&x| x)
-        })
+    pub fn Item(&self, index: u32) -> Option<JS<Attr>> {
+        self.owner.get().attrs.get_opt(index as uint).map(|x| x.clone())
     }
 
-    pub fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<@mut Attr> {
+    pub fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<JS<Attr>> {
         let item = self.Item(index);
         *found = item.is_some();
         item
diff --git a/src/components/script/dom/bindings/callback.rs b/src/components/script/dom/bindings/callback.rs
index 40b3bd7b5fa..10cb35c3af4 100644
--- a/src/components/script/dom/bindings/callback.rs
+++ b/src/components/script/dom/bindings/callback.rs
@@ -4,12 +4,15 @@
 
 use dom::bindings::utils::Reflectable;
 use js::jsapi::{JSContext, JSObject, JS_WrapObject, JSVal, JS_ObjectIsCallable};
-use js::jsapi::JS_GetProperty;
-use js::{JSVAL_IS_OBJECT, JSVAL_TO_OBJECT};
+use js::jsapi::{JS_GetProperty, JSTracer, JS_CallTracer};
+use js::{JSVAL_IS_OBJECT, JSVAL_TO_OBJECT, JSTRACE_OBJECT};
 
+use std::cast;
 use std::libc;
 use std::ptr;
 
+use extra::serialize::{Encodable, Encoder};
+
 pub enum ExceptionHandling {
     // Report any exception and don't throw it to the caller code.
     eReportExceptions,
@@ -26,6 +29,20 @@ pub struct CallbackInterface {
     callback: *JSObject
 }
 
+impl<S: Encoder> Encodable<S> for CallbackInterface {
+    fn encode(&self, s: &mut S) {
+        unsafe {
+            let tracer: *mut JSTracer = cast::transmute(s);
+            "callback".to_c_str().with_ref(|name| {
+                (*tracer).debugPrinter = ptr::null();
+                (*tracer).debugPrintIndex = -1;
+                (*tracer).debugPrintArg = name as *libc::c_void;
+                JS_CallTracer(tracer as *JSTracer, self.callback, JSTRACE_OBJECT as u32);
+            });
+        }
+    }
+}
+
 pub trait CallbackContainer {
     fn callback(&self) -> *JSObject;
 }
@@ -66,7 +83,7 @@ pub fn GetJSObjectFromCallback<T: CallbackContainer>(callback: &T) -> *JSObject
 
 pub fn WrapCallThisObject<T: 'static + CallbackContainer + Reflectable>(cx: *JSContext,
                                                                         _scope: *JSObject,
-                                                                        p: @mut T) -> *JSObject {
+                                                                        p: ~T) -> *JSObject {
     let obj = GetJSObjectFromCallback(p);
     assert!(obj.is_not_null());
 
diff --git a/src/components/script/dom/bindings/codegen/Bindings.conf b/src/components/script/dom/bindings/codegen/Bindings.conf
index b45eca71ba8..8485377ed8b 100644
--- a/src/components/script/dom/bindings/codegen/Bindings.conf
+++ b/src/components/script/dom/bindings/codegen/Bindings.conf
@@ -96,7 +96,6 @@ DOMInterfaces = {
 
 'Blob': [
 {
-    'headerFile': 'nsIDOMFile.h',
 },
 #{
 #    'workers': True,
@@ -121,19 +120,14 @@ DOMInterfaces = {
 }],
 
 'CharacterData': {
-    'nativeType': 'AbstractNode',
-    'concreteType': 'CharacterData',
-    'pointerType': ''
 },
 
 'ClientRect': [
 {
-    'nativeType': 'ClientRect',
 }],
 
 'ClientRectList': [
 {
-    'nativeType': 'ClientRectList',
 }],
 
 'Console': {
@@ -150,8 +144,6 @@ DOMInterfaces = {
 },
 
 'Document': {
-    'nativeType': 'AbstractDocument',
-    'pointerType': '',
     'customTrace': 'trace',
     'needsAbstract': [
         'createComment',
@@ -165,15 +157,12 @@ DOMInterfaces = {
 },
 
 'DOMException': {
-    'nativeType': 'DOMException',
 },
 
 'DOMImplementation': {
-    'nativeType': 'DOMImplementation',
 },
 
 'DOMParser': {
-    'nativeType': 'DOMParser',
 },
 
 'DOMSettableTokenList': [
@@ -195,15 +184,10 @@ DOMInterfaces = {
 }],
 
 'Element': {
-    'nativeType': 'AbstractNode',
-    'pointerType': '',
     'needsAbstract': ['getClientRects', 'getBoundingClientRect', 'setAttribute', 'setAttributeNS', 'removeAttribute', 'removeAttributeNS', 'id', 'attributes', 'innerHTML', 'outerHTML']
 },
 
 'Event': {
-    'nativeType': 'AbstractEvent',
-    'concreteType': 'Event',
-    'pointerType': '',
 },
 
 'EventListener': {
@@ -211,9 +195,6 @@ DOMInterfaces = {
 },
 
 'EventTarget': {
-    'nativeType': 'AbstractEventTarget',
-    'concreteType': 'EventTarget',
-    'pointerType': '',
     'needsAbstract': ['dispatchEvent']
 },
 
@@ -241,22 +222,8 @@ DOMInterfaces = {
 
 'HTMLCollection': [
 {
-    'nativeType': 'HTMLCollection',
-    'pointerType': '@mut '
 }],
 
-'HTMLDocument': {
-    'nativeType': 'AbstractDocument',
-    'pointerType': '',
-    'customTrace': 'trace'
-},
-
-'HTMLFormElement': {
-    'nativeType': 'AbstractNode',
-    'pointerType': '',
-    'register': False
-},
-
 'HTMLOptionsCollection': [
 {
     'nativeType': 'nsHTMLOptionCollection',
@@ -306,27 +273,21 @@ DOMInterfaces = {
 }],
 
 'MouseEvent': {
-    'nativeType': 'AbstractEvent',
-    'concreteType': 'MouseEvent',
-    'pointerType': '',
 },
 
 'Navigator': {
 },
 
 'Node': {
-    'nativeType': 'AbstractNode',
-    'concreteType': 'Node',
-    'pointerType': '',
     'needsAbstract': [
         'appendChild',
-        'insertBefore',
-        'replaceChild',
+        'childNodes',
+	'insertBefore',
         'nodeName',
         'nodeValue',
         'removeChild',
+        'replaceChild',
         'textContent',
-        'childNodes',
         'contains',
         'isEqualNode',
     ]
@@ -334,8 +295,6 @@ DOMInterfaces = {
 
 'NodeList': [
 {
-    'nativeType': 'NodeList',
-    'pointerType': '@mut ',
     'resultNotAddRefed': ['item']
 }],
 
@@ -410,9 +369,6 @@ DOMInterfaces = {
 }],
 
 'UIEvent': {
-    'nativeType': 'AbstractEvent',
-    'concreteType': 'UIEvent',
-    'pointerType': '',
 },
 
 'ValidityState': {
@@ -592,7 +548,7 @@ def addExternalIface(iface, nativeType=None, headerFile=None, pointerType=None):
 # FIXME: This should be renamed: https://github.com/mozilla/servo/issues/1625
 def addHTMLElement(element, concrete=None, needsAbstract=[]):
   DOMInterfaces[element] = {
-    'nativeType': 'AbstractNode',
+    'nativeType': 'JS<%s>' % element,
     'pointerType': '',
     'concreteType': concrete if concrete else element,
     'customTrace': 'trace',
diff --git a/src/components/script/dom/bindings/codegen/CodegenRust.py b/src/components/script/dom/bindings/codegen/CodegenRust.py
index bcd9a4a2de4..16ea49c38c0 100644
--- a/src/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/src/components/script/dom/bindings/codegen/CodegenRust.py
@@ -92,9 +92,13 @@ class CastableObjectUnwrapper():
 
     codeOnFailure is the code to run if unwrapping fails.
     """
-    def __init__(self, descriptor, source, target, codeOnFailure, isOptional=False):
+    def __init__(self, descriptor, source, target, codeOnFailure, isOptional=False,
+                 preUnwrapped=None, postUnwrapped=None):
         assert descriptor.castable
 
+        unwrappedVal = "val"
+        if preUnwrapped or postUnwrapped:
+            unwrappedVal = preUnwrapped + unwrappedVal + postUnwrapped
         self.substitution = { "type" : descriptor.nativeType,
                               "depth": descriptor.interface.inheritanceDepth(),
                               "prototype": "PrototypeList::id::" + descriptor.name,
@@ -102,7 +106,8 @@ class CastableObjectUnwrapper():
                               "source" : source,
                               "target" : target,
                               "codeOnFailure" : CGIndenter(CGGeneric(codeOnFailure), 4).define(),
-                              "unwrapped_val" : "Some(val)" if isOptional else "val" }
+                              "unwrapped_val" : ("Some(%s)" % unwrappedVal) if isOptional else unwrappedVal,
+                              "unwrapFn": "unwrap_jsmanaged" if 'JS' in descriptor.nativeType else "unwrap_object"}
         if descriptor.hasXPConnectImpls:
             # We don't use xpc_qsUnwrapThis because it will always throw on
             # unwrap failure, whereas we want to control whether we throw or
@@ -123,7 +128,7 @@ class CastableObjectUnwrapper():
 
     def __str__(self):
         return string.Template(
-"""match unwrap_object(${source}, ${prototype}, ${depth}) {
+"""match ${unwrapFn}(${source}, ${prototype}, ${depth}) {
   Ok(val) => ${target} = ${unwrapped_val},
   Err(()) => {
     ${codeOnFailure}
@@ -406,8 +411,7 @@ class FakeCastableDescriptor():
     def __init__(self, descriptor):
         self.castable = True
         self.workers = descriptor.workers
-        self.nativeType = descriptor.nativeType
-        self.pointerType = descriptor.pointerType
+        self.nativeType = "*Box<%s>" % descriptor.concreteType
         self.name = descriptor.name
         self.hasXPConnectImpls = descriptor.hasXPConnectImpls
         class FakeInterface:
@@ -447,7 +451,9 @@ def getJSToNativeConversionTemplate(type, descriptorProvider, failureCode=None,
                                     isClamp=False,
                                     exceptionCode=None,
                                     isCallbackReturnValue=False,
-                                    sourceDescription="value"):
+                                    sourceDescription="value",
+                                    preSuccess=None,
+                                    postSuccess=None):
     """
     Get a template for converting a JS value to a native object based on the
     given type and descriptor.  If failureCode is given, then we're actually
@@ -706,8 +712,8 @@ for (uint32_t i = 0; i < length; ++i) {
                (isinstance(defaultValue, IDLNullValue) and nullable))
 
         unionArgumentObj = "${holderName}"
-        if isOptional or nullable:
-            unionArgumentObj += ".ref()"
+        #if isOptional or nullable:
+        #    unionArgumentObj += ".get_mut_ref()"
 
         memberTypes = type.flatMemberTypes
         names = []
@@ -720,7 +726,7 @@ for (uint32_t i = 0; i < length; ++i) {
                     name = memberType.inner.identifier.name
                 else:
                     name = memberType.name
-                interfaceObject.append(CGGeneric("(failed = !%s.TrySetTo%s(cx, ${val}, ${valPtr}, tryNext)) || !tryNext" % (unionArgumentObj, name)))
+                interfaceObject.append(CGGeneric("{res = %s.TrySetTo%s(cx, ${val}, ${valPtr}); res.is_err() || !res.unwrap()}" % (unionArgumentObj, name)))
                 names.append(name)
             interfaceObject = CGWrapper(CGList(interfaceObject, " ||\n"), pre="done = ", post=";\n", reindent=True)
         else:
@@ -731,7 +737,7 @@ for (uint32_t i = 0; i < length; ++i) {
             assert len(arrayObjectMemberTypes) == 1
             memberType = arrayObjectMemberTypes[0]
             name = memberType.name
-            arrayObject = CGGeneric("done = (failed = !%s.TrySetTo%s(cx, ${val}, ${valPtr}, tryNext)) || !tryNext;" % (unionArgumentObj, name))
+            arrayObject = CGGeneric("done = {res = %s.TrySetTo%s(cx, ${val}, ${valPtr}); res.is_err() || !res.unwrap()};" % (unionArgumentObj, name))
             # XXX Now we're supposed to check for an array or a platform object
             # that supports indexed properties... skip that last for now. It's a
             # bit of a pain.
@@ -761,7 +767,7 @@ for (uint32_t i = 0; i < length; ++i) {
             assert len(callbackMemberTypes) == 1
             memberType = callbackMemberTypes[0]
             name = memberType.name
-            callbackObject = CGGeneric("done = (failed = !%s.TrySetTo%s(cx, ${val}, ${valPtr}, tryNext)) || !tryNext;" % (unionArgumentObj, name))
+            callbackObject = CGGeneric("done = {res = %s.TrySetTo%s(cx, ${val}, ${valPtr}); res.is_err() || !res.unwrap()};" % (unionArgumentObj, name))
             names.append(name)
         else:
             callbackObject = None
@@ -816,7 +822,7 @@ for (uint32_t i = 0; i < length; ++i) {
             if any([arrayObject, dateObject, nonPlatformObject, object]):
                 templateBody.prepend(CGGeneric("JSObject& argObj = ${val}.toObject();"))
             templateBody = CGWrapper(CGIndenter(templateBody),
-                                     pre="if (${val}.isObject()) {\n",
+                                     pre="if JSVAL_IS_OBJECT(${val}) {\n",
                                      post="\n}")
         else:
             templateBody = CGGeneric()
@@ -831,7 +837,7 @@ for (uint32_t i = 0; i < length; ++i) {
                 name = memberType.inner.identifier.name
             else:
                 name = memberType.name
-            other = CGGeneric("done = (failed = !%s.TrySetTo%s(cx, ${val}, ${valPtr}, tryNext)) || !tryNext;" % (unionArgumentObj, name))
+            other = CGGeneric("done = {res = %s.TrySetTo%s(cx, ${val}, ${valPtr}); res.is_err() || !res.unwrap()};" % (unionArgumentObj, name))
             names.append(name)
             if hasObjectTypes:
                 other = CGWrapper(CGIndenter(other), "{\n", post="\n}")
@@ -844,28 +850,25 @@ for (uint32_t i = 0; i < length; ++i) {
         else:
             other = None
 
-        templateBody = CGWrapper(templateBody, pre="bool done = false, failed = false, tryNext;\n")
-        throw = CGGeneric("if (failed) {\n"
-                          "  return false;\n"
+        templateBody = CGWrapper(templateBody, pre="let mut done = false;\n"
+                                 "let mut res = Ok(true);\n")
+        throw = CGGeneric("if res.is_err() {\n"
+                          "  return 0;\n"
                           "}\n"
-                          "if (!done) {\n"
-                          "  return ThrowErrorMessage(cx, MSG_NOT_IN_UNION, \"%s\");\n"
+                          "if !done {\n"
+                          "  return throw_not_in_union(cx, \"%s\");\n"
                           "}" % ", ".join(names))
         templateBody = CGWrapper(CGIndenter(CGList([templateBody, throw], "\n")), pre="{\n", post="\n}")
 
         typeName = type.name
         argumentTypeName = typeName + "Argument"
         if nullable:
-            typeName = "Nullable<" + typeName + " >"
-        if isOptional:
-            nonConstDecl = "const_cast<Optional<" + typeName + " >& >(${declName})"
-        else:
-            nonConstDecl = "const_cast<" + typeName + "& >(${declName})"
-            typeName = "const " + typeName
+            typeName = "Option<" + typeName + " >"
+        nonConstDecl = "${declName}"
 
         def handleNull(templateBody, setToNullVar, extraConditionForNull=""):
-            null = CGGeneric("if (%s${val}.isNullOrUndefined()) {\n"
-                             "  %s.SetNull();\n"
+            null = CGGeneric("if %s(RUST_JSVAL_IS_NULL(${val}) != 0 || RUST_JSVAL_IS_VOID(${val}) != 0) {\n"
+                             "  %s = None;\n"
                              "}" % (extraConditionForNull, setToNullVar))
             templateBody = CGWrapper(CGIndenter(templateBody), pre="{\n", post="\n}")
             return CGList([null, templateBody], " else ")
@@ -878,21 +881,24 @@ for (uint32_t i = 0; i < length; ++i) {
         if isOptional:
             mutableDecl = nonConstDecl + ".Value()"
             declType = CGWrapper(declType, pre="const Optional<", post=" >")
-            holderType = CGWrapper(holderType, pre="Maybe<", post=" >")
+            holderType = CGWrapper(holderType, pre="Option<", post=" >")
             constructDecl = CGGeneric(nonConstDecl + ".Construct();")
             if nullable:
-                constructHolder = CGGeneric("${holderName}.construct(%s.SetValue());" % mutableDecl)
+                constructHolder = CGGeneric("${holderName} = Some(%s.SetValue());" % mutableDecl)
             else:
-                constructHolder = CGGeneric("${holderName}.construct(${declName}.Value());")
+                constructHolder = CGGeneric("${holderName} = Some(${declName}.Value());")
         else:
             mutableDecl = nonConstDecl
             constructDecl = None
+            holderInit = "${declName}"
             if nullable:
-                holderType = CGWrapper(holderType, pre="Maybe<", post=" >")
-                constructHolder = CGGeneric("${holderName}.construct(%s.SetValue());" % mutableDecl)
+                holderInit += ".get_mut_ref()"
             else:
-                constructHolder = CGWrapper(holderType, post=" ${holderName}(${declName});")
-                holderType = None
+                holderInit = "&mut " + holderInit
+            constructHolder = CGWrapper(holderType, pre="let mut ${holderName} = ", post="::new(" + holderInit + ");")
+            if nullable:
+                constructHolder = CGWrapper(constructHolder, pre="${declName} = Some(uninit());\n")
+            holderType = None
 
         templateBody = CGList([constructHolder, templateBody], "\n")
         if nullable:
@@ -903,9 +909,10 @@ for (uint32_t i = 0; i < length; ++i) {
                 valueMissing = ""
             templateBody = handleNull(templateBody, mutableDecl,
                                       extraConditionForNull=valueMissing)
-        templateBody = CGList([constructDecl, templateBody], "\n")
+        templateBody = CGWrapper(CGIndenter(CGList([constructDecl, templateBody], "\n")),
+                                 pre="{\n", post="\n}")
 
-        return templateBody.define(), declType, holderType, False, None
+        return templateBody.define(), declType, holderType, False, "uninit()" if not nullable else None
 
     if type.isGeckoInterface():
         assert not isEnforceRange and not isClamp
@@ -934,8 +941,7 @@ for (uint32_t i = 0; i < length; ++i) {
         forceOwningType = (descriptor.interface.isCallback() and
                            not descriptor.workers) or isMember
 
-        typeName = descriptor.nativeType
-        typePtr = descriptor.pointerType + typeName
+        typePtr = descriptor.nativeType
 
         # Compute a few things:
         #  - declType is the type we want to return as the first element of our
@@ -969,7 +975,8 @@ for (uint32_t i = 0; i < length; ++i) {
                         "JSVAL_TO_OBJECT(${val})",
                         "${declName}",
                         failureCode,
-                        isOptional or argIsPointer or type.nullable()))
+                        isOptional or argIsPointer or type.nullable(),
+                        preUnwrapped=preSuccess, postUnwrapped=postSuccess))
             else:
                 templateBody += str(FailureFatalCastableObjectUnwrapper(
                         descriptor,
@@ -1255,32 +1262,41 @@ for (uint32_t i = 0; i < length; ++i) {
     elif isClamp:
         conversionBehavior = "eClamp"
 
+    if failureCode is None:
+        failureCode = 'return 0'
+
     if type.nullable():
         dataLoc = "${declName}.SetValue()"
         nullCondition = "(RUST_JSVAL_IS_NULL(${val}) != 0 || RUST_JSVAL_IS_VOID(${val}) != 0)"
         if defaultValue is not None and isinstance(defaultValue, IDLNullValue):
             nullCondition = "!(${haveValue}) || " + nullCondition
+        successVal = "val_"
+        if preSuccess or postSuccess:
+            successVal = preSuccess + successVal + postSuccess
         #XXXjdm support conversionBehavior here
         template = (
             "if (%s) {\n"
             "  ${declName} = None;\n"
             "} else {\n"
             "  match JSValConvertible::from_jsval(${val}) {\n"
-            "    Some(val_) => ${declName} = Some(val_),\n"
-            "    None => return 0\n"
+            "    Some(val_) => ${declName} = Some(%s),\n"
+            "    None => %s\n"
             "  }\n"
-           "}" % nullCondition)
+           "}" % (nullCondition, successVal, failureCode))
         declType = CGGeneric("Option<" + typeName + ">")
     else:
         assert(defaultValue is None or
                not isinstance(defaultValue, IDLNullValue))
         dataLoc = "${declName}"
         #XXXjdm conversionBehavior should be used
+        successVal = "v"
+        if preSuccess or postSuccess:
+            successVal = preSuccess + successVal + postSuccess
         template = (
             "match JSValConvertible::from_jsval(${val}) {\n"
-            "  None => return 0,\n"
-            "  Some(v) => %s = v\n"
-            "}" % (dataLoc,))
+            "  None => %s,\n"
+            "  Some(v) => %s = %s\n"
+            "}" % (failureCode, dataLoc, successVal))
         declType = CGGeneric(typeName)
     if (defaultValue is not None and
         # We already handled IDLNullValue, so just deal with the other ones
@@ -1730,9 +1746,7 @@ def getRetvalDeclarationForType(returnType, descriptorProvider,
             returnType.unroll().inner.identifier.name)
         result = CGGeneric(descriptor.nativeType)
         if returnType.nullable():
-            result = CGWrapper(result, pre=("Option<" + descriptor.pointerType), post=">")
-        else:
-            result = CGWrapper(result, pre=descriptor.pointerType)
+            result = CGWrapper(result, pre="Option<", post=">")
         return result, False
     if returnType.isCallback():
         # XXXbz we're going to assume that callback types are always
@@ -2388,6 +2402,112 @@ class CGGeneric(CGThing):
     def define(self):
         return self.defineText
 
+def getTypes(descriptor):
+    """
+    Get all argument and return types for all members of the descriptor
+    """
+    members = [m for m in descriptor.interface.members]
+    if descriptor.interface.ctor():
+        members.append(descriptor.interface.ctor())
+    signatures = [s for m in members if m.isMethod() for s in m.signatures()]
+    types = []
+    for s in signatures:
+        assert len(s) == 2
+        (returnType, arguments) = s
+        types.append(returnType)
+        types.extend([a.type for a in arguments])
+
+    types.extend(a.type for a in members if a.isAttr())
+    return types
+
+def SortedTuples(l):
+    """
+    Sort a list of tuples based on the first item in the tuple
+    """
+    return sorted(l, key=operator.itemgetter(0))
+
+def SortedDictValues(d):
+    """
+    Returns a list of values from the dict sorted by key.
+    """
+    # Create a list of tuples containing key and value, sorted on key.
+    d = SortedTuples(d.items())
+    # We're only interested in the values.
+    return (i[1] for i in d)
+
+def UnionTypes(descriptors):
+    """
+    Returns a tuple containing a set of header filenames to include, a set of
+    tuples containing a type declaration and a boolean if the type is a struct
+    for member types of the unions and a CGList containing CGUnionStructs for
+    every union.
+    """
+
+    # Now find all the things we'll need as arguments and return values because
+    # we need to wrap or unwrap them.
+    headers = set()
+    declarations = set()
+    unionStructs = dict()
+    for d in descriptors:
+        if d.interface.isExternal():
+            continue
+
+        for t in getTypes(d):
+            t = t.unroll()
+            if t.isUnion():
+                name = str(t)
+                if not name in unionStructs:
+                    unionStructs[name] = CGUnionStruct(t, d)
+                    for f in t.flatMemberTypes:
+                        f = f.unroll()
+                        if f.isInterface():
+                            if f.isSpiderMonkeyInterface():
+                                headers.add("jsfriendapi.h")
+                                headers.add("mozilla/dom/TypedArray.h")
+                            else:
+                                typeDesc = d.getDescriptor(f.inner.identifier.name)
+                                if typeDesc is not None:
+                                    declarations.add((typeDesc.nativeType, False))
+                        elif f.isDictionary():
+                            declarations.add((f.inner.identifier.name, True))
+
+    return (headers, declarations, CGList(SortedDictValues(unionStructs), "\n"))
+
+def UnionConversions(descriptors):
+    """
+    Returns a CGThing to declare all union argument conversion helper structs.
+    """
+    # Now find all the things we'll need as arguments because we
+    # need to unwrap them.
+    unionConversions = dict()
+    for d in descriptors:
+        if d.interface.isExternal():
+            continue
+
+        def addUnionTypes(type):
+            if type.isUnion():
+                type = type.unroll()
+                name = str(type)
+                if not name in unionConversions:
+                    unionConversions[name] = CGUnionConversionStruct(type, d)
+
+        members = [m for m in d.interface.members]
+        if d.interface.ctor():
+            members.append(d.interface.ctor())
+        signatures = [s for m in members if m.isMethod() for s in m.signatures()]
+        for s in signatures:
+            assert len(s) == 2
+            (_, arguments) = s
+            for a in arguments:
+                addUnionTypes(a.type)
+
+        for m in members:
+            if m.isAttr() and not m.readonly:
+                addUnionTypes(m.type)
+
+    return CGWrapper(CGList(SortedDictValues(unionConversions), "\n"),
+                     post="\n\n")
+
 class Argument():
     """
     A class for outputting the type and name of an argument
@@ -2497,33 +2617,40 @@ class CGAbstractMethod(CGThing):
     def definition_body(self):
         assert(False) # Override me!
 
+def DOMObjectPointerType(descriptor):
+    return "~"
+
+def DOMObjectPointerArg(descriptor):
+    return DOMObjectPointerType(descriptor) + descriptor.concreteType
+
 def CreateBindingJSObject(descriptor, parent=None):
+    create = "  let raw: *mut %s = &mut *aObject;\n" % descriptor.concreteType;
     if descriptor.proxy:
         assert not descriptor.createGlobal
         handler = """
   let page = page_from_context(aCx);
   let handler = (*page).js_info.get_ref().dom_static.proxy_handlers.get(&(PrototypeList::id::%s as uint));
 """ % descriptor.name
-        create = handler + """  let obj = NewProxyObject(aCx, *handler,
-                           ptr::to_unsafe_ptr(&RUST_PRIVATE_TO_JSVAL(squirrel_away(aObject) as *libc::c_void)),
+        create += handler + """  let obj = NewProxyObject(aCx, *handler,
+                           ptr::to_unsafe_ptr(&RUST_PRIVATE_TO_JSVAL(squirrel_away_unique(aObject) as *libc::c_void)),
                            proto, %s,
                            ptr::null(), ptr::null());
   if obj.is_null() {
     return ptr::null();
   }
 
-""" % parent
+""" % (parent)
     else:
         if descriptor.createGlobal:
-            create = "  let obj = CreateDOMGlobal(aCx, &Class.base);\n"
+            create += "  let obj = CreateDOMGlobal(aCx, &Class.base);\n"
         else:
-            create = "  let obj = JS_NewObject(aCx, &Class.base, proto, %s);\n" % parent
+            create += "  let obj = JS_NewObject(aCx, &Class.base, proto, %s);\n" % parent
         create += """  if obj.is_null() {
     return ptr::null();
   }
 
   JS_SetReservedSlot(obj, DOM_OBJECT_SLOT as u32,
-                     RUST_PRIVATE_TO_JSVAL(squirrel_away(aObject) as *libc::c_void));
+                     RUST_PRIVATE_TO_JSVAL(squirrel_away_unique(aObject) as *libc::c_void));
 """
     return create
 
@@ -2531,7 +2658,7 @@ class CGWrapWithCacheMethod(CGAbstractMethod):
     def __init__(self, descriptor):
         assert descriptor.interface.hasInterfacePrototypeObject()
         args = [Argument('*JSContext', 'aCx'), Argument('*JSObject', 'aScope'),
-                Argument('@mut ' + descriptor.concreteType, 'aObject')]
+                Argument(DOMObjectPointerArg(descriptor), 'aObject', mutable=True)]
         CGAbstractMethod.__init__(self, descriptor, 'Wrap_', '*JSObject', args)
 
     def definition_body(self):
@@ -2548,20 +2675,20 @@ class CGWrapWithCacheMethod(CGAbstractMethod):
   if proto.is_null() {
     return ptr::null();
   }
-%s
 
-  //NS_ADDREF(aObject);
+%s
 
-  aObject.mut_reflector().set_jsobject(obj);
+  (*raw).mut_reflector().set_jsobject(obj);
 
-  return obj;""" % (CreateBindingJSObject(self.descriptor, "aScope"))
+  return obj;""" % CreateBindingJSObject(self.descriptor, "aScope")
         else:
             return """
   assert!(aScope.is_null());
+
 %s
   let proto = GetProtoObject(aCx, obj, obj);
   JS_SetPrototype(aCx, obj, proto);
-  aObject.mut_reflector().set_jsobject(obj);
+  (*raw).mut_reflector().set_jsobject(obj);
   return obj;""" % CreateBindingJSObject(self.descriptor)
 
 class CGWrapMethod(CGAbstractMethod):
@@ -2569,7 +2696,7 @@ class CGWrapMethod(CGAbstractMethod):
         # XXX can we wrap if we don't have an interface prototype object?
         assert descriptor.interface.hasInterfacePrototypeObject()
         args = [Argument('*JSContext', 'aCx'), Argument('*JSObject', 'aScope'),
-                Argument('@mut ' + descriptor.concreteType, 'aObject')]
+                Argument(DOMObjectPointerArg(descriptor), 'aObject', mutable=True)]
         CGAbstractMethod.__init__(self, descriptor, 'Wrap', '*JSObject', args, inline=True, pub=True)
 
     def definition_body(self):
@@ -2961,7 +3088,11 @@ class CGCallGenerator(CGThing):
             if a.type.isObject() and not a.type.nullable() and not a.optional:
                 name = "(JSObject&)" + name
             #XXXjdm Perhaps we should pass all nontrivial types by borrowed pointer
-            if a.type.isDictionary():
+            if a.type.isGeckoInterface():
+                argDescriptor = descriptorProvider.getDescriptor(a.type.name)
+                if not (a.type.nullable() or a.optional):
+                    name = "&mut " + name
+            elif a.type.isDictionary():
                 name = "&" + name
             args.append(CGGeneric(name))
 
@@ -3288,8 +3419,8 @@ class CGSpecializedMethod(CGAbstractExternMethod):
         argsPre = []
         if name in self.descriptor.needsAbstract:
             abstractName = re.sub(r'<\w+>', '', self.descriptor.nativeType)
-            extraPre = '  let abstract_this = %s::from_box(this);\n' % abstractName
-            argsPre = ['abstract_this']
+            extraPre = '  let mut abstract_this = %s::from_box(this);\n' % abstractName
+            argsPre = ['&mut abstract_this']
         return CGWrapper(CGMethodCall(argsPre, nativeName, self.method.isStatic(),
                                       self.descriptor, self.method),
                          pre=extraPre +
@@ -3317,8 +3448,10 @@ class CGGenericGetter(CGAbstractBindingMethod):
 
     def generate_code(self):
         return CGIndenter(CGGeneric(
-            "let info: *JSJitInfo = RUST_FUNCTION_VALUE_TO_JITINFO(JS_CALLEE(cx, &*vp));\n"
-            "return CallJitPropertyOp(info, cx, obj, this as *libc::c_void, &*vp);"))
+            "return with_gc_disabled(cx, || {\n"
+            "  let info: *JSJitInfo = RUST_FUNCTION_VALUE_TO_JITINFO(JS_CALLEE(cx, &*vp));\n"
+            "  CallJitPropertyOp(info, cx, obj, this as *libc::c_void, &*vp)\n"
+            "});\n"))
 
 class CGSpecializedGetter(CGAbstractExternMethod):
     """
@@ -3348,8 +3481,8 @@ class CGSpecializedGetter(CGAbstractExternMethod):
                                                             getter=True))
         if name in self.descriptor.needsAbstract:
             abstractName = re.sub(r'<\w+>', '', self.descriptor.nativeType)
-            extraPre = '  let abstract_this = %s::from_box(this);\n' % abstractName
-            argsPre = ['abstract_this']
+            extraPre = '  let mut abstract_this = %s::from_box(this);\n' % abstractName
+            argsPre = ['&mut abstract_this']
         if resultOutParam or self.attr.type.nullable() or not infallible:
             nativeName = "Get" + nativeName
         return CGWrapper(CGIndenter(CGGetterCall(argsPre, self.attr.type, nativeName,
@@ -3381,7 +3514,10 @@ class CGGenericSetter(CGAbstractBindingMethod):
                 "let undef = JSVAL_VOID;\n"
                 "let argv: *JSVal = if argc != 0 { JS_ARGV(cx, vp as *JSVal) } else { &undef as *JSVal };\n"
                 "let info: *JSJitInfo = RUST_FUNCTION_VALUE_TO_JITINFO(JS_CALLEE(cx, vp as *JSVal));\n"
-                "if CallJitPropertyOp(info, cx, obj, this as *libc::c_void, argv) == 0 {"
+                "let ok = with_gc_disabled(cx, || {\n"
+                "  CallJitPropertyOp(info, cx, obj, this as *libc::c_void, argv)\n"
+                "});\n"
+                "if ok == 0 {\n"
                 "  return 0;\n"
                 "}\n"
                 "*vp = JSVAL_VOID;\n"
@@ -3408,8 +3544,8 @@ class CGSpecializedSetter(CGAbstractExternMethod):
         extraPre = ''
         if name in self.descriptor.needsAbstract:
             abstractName = re.sub(r'<\w+>', '', self.descriptor.nativeType)
-            extraPre = '  let abstract_this = %s::from_box(this);\n' % abstractName
-            argsPre = ['abstract_this']
+            extraPre = '  let mut abstract_this = %s::from_box(this);\n' % abstractName
+            argsPre = ['&mut abstract_this']
         return CGWrapper(CGIndenter(CGSetterCall(argsPre, self.attr.type, nativeName,
                                                  self.descriptor, self.attr)),
                          pre=extraPre +
@@ -3531,6 +3667,282 @@ class CGEnum(CGThing):
 """ % (",\n    ".join(map(getEnumValueName, self.enum.values())),
        ",\n    ".join(['EnumEntry {value: &"' + val + '", length: ' + str(len(val)) + '}' for val in self.enum.values()]))
 
+def getUnionAccessorSignatureType(type, descriptorProvider):
+    """
+    Returns the types that are used in the getter and setter signatures for
+    union types
+    """
+    if type.isArray():
+        raise TypeError("Can't handle array arguments yet")
+
+    if type.isSequence():
+        nullable = type.nullable();
+        if nullable:
+            type = type.inner.inner
+        else:
+            type = type.inner
+        (elementTemplate, elementDeclType,
+         elementHolderType, dealWithOptional) = getJSToNativeConversionTemplate(
+            type, descriptorProvider, isSequenceMember=True)
+        typeName = CGWrapper(elementDeclType, pre="Sequence< ", post=" >&")
+        if nullable:
+            typeName = CGWrapper(typeName, pre="Nullable< ", post=" >&")
+
+        return typeName
+
+    if type.isUnion():
+        typeName = CGGeneric(type.name)
+        if type.nullable():
+            typeName = CGWrapper(typeName, pre="Nullable< ", post=" >&")
+
+        return typeName
+
+    if type.isGeckoInterface():
+        descriptor = descriptorProvider.getDescriptor(
+            type.unroll().inner.identifier.name)
+        typeName = CGGeneric(descriptor.nativeType)
+        # Allow null pointers for nullable types and old-binding classes
+        if type.nullable() or type.unroll().inner.isExternal():
+            typeName = CGWrapper(typeName, pre="Option<", post=">")
+        else:
+            typeName = CGWrapper(typeName, pre="&'a ")
+        return typeName
+
+    if type.isSpiderMonkeyInterface():
+        typeName = CGGeneric(type.name)
+        if type.nullable():
+            typeName = CGWrapper(typeName, pre="Option<", post=">")
+        else:
+            typeName = CGWrapper(typeName, pre="&")
+        return typeName
+
+    if type.isString():
+        return CGGeneric("const nsAString&")
+
+    if type.isEnum():
+        if type.nullable():
+            raise TypeError("We don't support nullable enumerated arguments or "
+                            "union members yet")
+        return CGGeneric(type.inner.identifier.name)
+
+    if type.isCallback():
+        return CGGeneric("JSObject*")
+
+    if type.isAny():
+        return CGGeneric("JS::Value")
+
+    if type.isObject():
+        typeName = CGGeneric("JSObject")
+        if type.nullable():
+            typeName = CGWrapper(typeName, post="*")
+        else:
+            typeName = CGWrapper(typeName, post="&")
+        return typeName
+
+    if not type.isPrimitive():
+        raise TypeError("Need native type for argument type '%s'" % str(type))
+
+    typeName = CGGeneric(builtinNames[type.tag()])
+    if type.nullable():
+        typeName = CGWrapper(typeName, pre="Nullable< ", post=" >&")
+    return typeName
+
+def getUnionTypeTemplateVars(type, descriptorProvider):
+    # For dictionaries and sequences we need to pass None as the failureCode
+    # for getJSToNativeConversionTemplate.
+    # Also, for dictionaries we would need to handle conversion of
+    # null/undefined to the dictionary correctly.
+    if type.isDictionary() or type.isSequence():
+        raise TypeError("Can't handle dictionaries or sequences in unions")
+
+    if type.isGeckoInterface():
+        name = type.inner.identifier.name
+        typeName = descriptorProvider.getDescriptor(name).nativeType
+    elif type.isEnum():
+        name = type.inner.identifier.name
+        typeName = name
+    elif type.isArray() or type.isSequence():
+        name = str(type)
+        #XXXjdm dunno about typeName here
+        typeName = "/*" + type.name + "*/"
+    elif type.isPrimitive():
+        name = type.name
+        typeName = builtinNames[type.tag()]
+    else:
+        name = type.name
+        typeName = "/*" + type.name + "*/"
+
+    tryNextCode = """{
+  return Ok(true);
+}"""
+    (template, declType, holderType,
+     dealWithOptional, initialValue) = getJSToNativeConversionTemplate(
+        type, descriptorProvider, failureCode=tryNextCode,
+        isDefinitelyObject=True, isOptional=type.nullable(), preSuccess="e" + name + "(", postSuccess=")")
+
+    structType = declType.define()
+    externalType = getUnionAccessorSignatureType(type, descriptorProvider).define()
+
+    if type.isObject():
+        setter = CGGeneric("pub fn SetToObject(obj: *JSObject) {\n"
+                           "  mUnion = Some(eObject(obj));\n"
+                           "}")
+    else:
+        jsConversion = string.Template(template).substitute(
+            {
+                "val": "value",
+                "valPtr": "pvalue",
+                "declName": "*self.mUnion",
+                "holderName": "m" + name + "Holder"
+                }
+            )
+        jsConversion = CGWrapper(CGGeneric(jsConversion),
+                                 post="\n"
+                                      "return Ok(false);")
+        setter = CGWrapper(CGIndenter(jsConversion),
+                           pre="pub fn TrySetTo" + name + "(&mut self, cx: *JSContext, value: JSVal, pvalue: *JSVal) -> Result<bool,()> {\n",
+                           post="\n"
+                                "}")
+
+    return {
+                "name": name,
+                "typeName": typeName,
+                "structType": structType,
+                "externalType": externalType,
+                "optRef": 'ref ' if externalType[0] == '&' else '',
+                "setter": CGIndenter(setter).define(),
+                "holderType": holderType.define() if holderType else None
+                }
+
+def mapTemplate(template, templateVarArray):
+    return map(lambda v: string.Template(template).substitute(v),
+               templateVarArray)
+
+class CGUnionStruct(CGThing):
+    def __init__(self, type, descriptorProvider):
+        CGThing.__init__(self)
+        self.type = type.unroll()
+        self.descriptorProvider = descriptorProvider
+
+    def declare(self):
+        templateVars = map(lambda t: getUnionTypeTemplateVars(t, self.descriptorProvider),
+                           self.type.flatMemberTypes)
+
+        callDestructors = []
+        enumValues = []
+        methods = []
+        if self.type.hasNullableType:
+            callDestructors.append("      case eNull:\n"
+                                   "        break;")
+            enumValues.append("eNull")
+            methods.append("""  pub fn IsNull(&self) -> bool {
+    match *self {
+      eNull => true,
+      _ => false
+    }
+  }""")
+
+        destructorTemplate = """  fn Destroy${name}(&mut self) {
+    assert!(Is${name}(), "Wrong type!");
+    *self.mUnion = None;
+  }"""
+        destructors = mapTemplate(destructorTemplate, templateVars)
+        callDestructors.extend(mapTemplate("      case e${name}:\n"
+                                           "         Destroy${name}();\n"
+                                           "         break;", templateVars))
+        enumValues.extend(mapTemplate("e${name}(${typeName})", templateVars))
+        methodTemplate = """  pub fn Is${name}(&self) -> bool {
+    match *self {
+      e${name}(_) => true,
+      _ => false
+    }
+  }
+  pub fn GetAs${name}<'a>(&'a self) -> ${externalType} {
+    assert!(self.Is${name}());
+    match *self {
+      e${name}(${optRef}inner) => inner,
+      _ => unreachable!()
+    }
+  }"""
+        methods.extend(mapTemplate(methodTemplate, templateVars))
+        values = mapTemplate("UnionMember<${structType} > m${name};", templateVars)
+        return string.Template("""
+pub enum ${structName} {
+  ${enumValues}
+}
+
+impl ${structName} {
+${methods}
+}
+""").substitute(
+    {
+       "structName": self.type.__str__(),
+       "callDestructors": "\n".join(callDestructors),
+       "destructors": "\n".join(destructors),
+       "methods": "\n\n".join(methods),
+       "enumValues": ",\n    ".join(enumValues),
+       "values": "\n    ".join(values),
+       })
+
+    def define(self):
+        return """
+"""
+
+class CGUnionConversionStruct(CGThing):
+    def __init__(self, type, descriptorProvider):
+        CGThing.__init__(self)
+        self.type = type.unroll()
+        self.descriptorProvider = descriptorProvider
+
+    def declare(self):
+        setters = []
+
+        if self.type.hasNullableType:
+            setters.append("""  pub fn SetNull(&mut self) -> bool
+  {
+    mUnion = Some(eNull);
+    return true;
+  }""")
+
+        templateVars = map(lambda t: getUnionTypeTemplateVars(t, self.descriptorProvider),
+                           self.type.flatMemberTypes)
+        structName = self.type.__str__()
+
+        setters.extend(mapTemplate("${setter}", templateVars))
+        private = "\n".join(mapTemplate("""  fn SetAs${name}() -> &${structType}
+  {
+    mUnion.mType = mUnion.e${name};
+    return mUnion.mValue.m${name}.SetValue();
+  }""", templateVars))
+        private += "\n\n"
+        holders = filter(lambda v: v["holderType"] is not None, templateVars)
+        if len(holders) > 0:
+            private += "\n".join(mapTemplate("  ${holderType} m${name}Holder;", holders))
+            private += "\n\n"
+        private += "  " + structName + "& mUnion;"
+        return string.Template("""
+pub struct ${structName}Argument<'a> {
+  mUnion: &'a mut ${innerType}
+}
+
+impl<'a> ${structName}Argument<'a> {
+  pub fn new(union: &'a mut ${innerType}) -> ${structName}Argument<'a> {
+    ${structName}Argument {
+      mUnion: union
+    }
+  }
+
+${setters}
+}
+""").substitute({"structName": structName,
+       "innerType": ("Option<%s>" % structName) if self.type.nullable() else structName,
+       "setters": "\n\n".join(setters),
+       })
+
+    def define(self):
+        return """
+"""
+
 class ClassItem:
     """ Use with CGClass """
     def __init__(self, name, visibility):
@@ -4482,9 +4894,9 @@ def finalizeHook(descriptor, hookName, context):
     else:
         assert descriptor.nativeIsISupports
         release = """let val = JS_GetReservedSlot(obj, dom_object_slot(obj));
-let _: @mut %s = cast::transmute(RUST_JSVAL_TO_PRIVATE(val));
+let _: %s %s = cast::transmute(RUST_JSVAL_TO_PRIVATE(val));
 debug!("%s finalize: {:p}", this);
-""" % (descriptor.concreteType, descriptor.concreteType)
+""" % (DOMObjectPointerType(descriptor), descriptor.concreteType, descriptor.concreteType)
     #return clearWrapper + release
     return release
 
@@ -4530,10 +4942,10 @@ class CGClassConstructHook(CGAbstractExternMethod):
   //       or through unwrapping a slot or something). We'll punt and get the Window
   //       from the context for now. 
   let page = page_from_context(cx);
-  let global = (*page).frame.get_ref().window;
+  let global = (*page).frame.get_ref().window.clone();
   let obj = global.reflector().get_jsobject();
 """
-            preArgs = ["global"]
+            preArgs = ["&global"]
 
         name = self._ctor.identifier.name
         nativeName = MakeNativeName(self.descriptor.binaryNames.get(name, name))
@@ -5151,17 +5563,16 @@ class CGBindingRoot(CGThing):
                           'js::jsfriendapi::bindgen::*',
                           'js::glue::*',
                           'dom::types::*',
+                          'dom::bindings::js::JS',
                           'dom::bindings::utils::*',
                           'dom::bindings::callback::*',
                           'dom::bindings::conversions::*',
                           'dom::bindings::codegen::*', #XXXjdm
+                          'dom::bindings::codegen::UnionTypes::*', #XXXjdm
+                          'dom::bindings::codegen::UnionConversions::*', #XXXjdm
                           'script_task::{JSPageInfo, page_from_context}',
                           'dom::bindings::proxyhandler',
                           'dom::bindings::proxyhandler::*',
-                          'dom::document::AbstractDocument',
-                          'dom::node::AbstractNode',
-                          'dom::eventtarget::AbstractEventTarget',
-                          'dom::event::AbstractEvent',
                           'servo_util::str::DOMString',
                           'servo_util::vec::zip_copies',
                           'std::cast',
@@ -5170,6 +5581,7 @@ class CGBindingRoot(CGThing):
                           'std::vec',
                           'std::str',
                           'std::num',
+                          'std::unstable::intrinsics::uninit',
                           'std::unstable::raw::Box',
                          ], 
                          [],
@@ -5427,9 +5839,9 @@ class CGNativeMember(ClassMethod):
                     else:
                         typeDecl = "NonNull<%s>"
                 else:
-                    typeDecl = "%s%s"
+                    typeDecl = "%s"
             descriptor = self.descriptorProvider.getDescriptor(iface.identifier.name)
-            return (typeDecl % (descriptor.pointerType, descriptor.nativeType),
+            return (typeDecl % descriptor.nativeType,
                     False, False)
 
         if type.isSpiderMonkeyInterface():
@@ -5560,7 +5972,7 @@ class CGCallback(CGClass):
                          bases=[ClassBase(baseName)],
                          constructors=self.getConstructors(),
                          methods=realMethods+getters+setters,
-                         decorators="#[deriving(Eq,Clone)]")
+                         decorators="#[deriving(Eq,Clone,Encodable)]")
 
     def getConstructors(self):
         return [ClassConstructor(
@@ -5591,20 +6003,19 @@ class CGCallback(CGClass):
         args.append(Argument("ExceptionHandling", "aExceptionHandling",
                              "eReportExceptions"))
 
-        # Ensure the first argument is mutable
-        args[0] = Argument(args[0].argType, args[0].name, args[0].default, mutable=True)
+        args[0] = Argument('&' + args[0].argType, args[0].name, args[0].default)
         method.args[2] = args[0]
 
         # And now insert our template argument.
         argsWithoutThis = list(args)
-        args.insert(0, Argument("@mut T",  "thisObj"))
+        args.insert(0, Argument("~T",  "thisObj"))
 
         # And the self argument
         method.args.insert(0, Argument(None, "&self"))
         args.insert(0, Argument(None, "&self"))
         argsWithoutThis.insert(0, Argument(None, "&self"))
 
-        setupCall = ("let s = CallSetup::new(cx_for_dom_object(&mut ${cxProvider}), aExceptionHandling);\n"
+        setupCall = ("let s = CallSetup::new(cx_for_dom_object(${cxProvider}), aExceptionHandling);\n"
                      "if s.GetContext().is_null() {\n"
                      "  return${errorReturn};\n"
                      "}\n")
@@ -5619,7 +6030,7 @@ class CGCallback(CGClass):
                 "errorReturn" : method.getDefaultRetval(),
                 "callArgs" : ", ".join(argnamesWithThis),
                 "methodName": 'self.' + method.name,
-                "cxProvider": '*thisObj'
+                "cxProvider": 'thisObj'
                 })
         bodyWithoutThis = string.Template(
             setupCall +
@@ -5954,8 +6365,14 @@ class CallbackMethod(CallbackMember):
             replacements["argv"] = "nullptr"
             replacements["argc"] = "0"
         return string.Template("${getCallable}"
-                "if unsafe { JS_CallFunctionValue(cx, ${thisObj}, callable,\n"
-                "                        ${argc}, ${argv}, &rval) == 0 } {\n"
+                "let ok = unsafe {\n"
+                "  //JS_AllowGC(cx); // It's unsafe to enable GC at arbitrary points during Rust execution; leave it disabled\n"
+                "  let ok = JS_CallFunctionValue(cx, ${thisObj}, callable,\n"
+                "                                ${argc}, ${argv}, &rval);\n"
+                "  //JS_InhibitGC(cx);\n"
+                "  ok\n"
+                "};\n"
+                "if ok == 0 {\n"
                 "  return${errorReturn};\n"
                 "}\n").substitute(replacements)
 
@@ -6176,3 +6593,152 @@ class GlobalGenRoots():
         curr = CGList([CGGeneric(declare="pub mod %sBinding;\n" % name) for name in descriptors])
         curr = CGWrapper(curr, pre=AUTOGENERATED_WARNING_COMMENT)
         return curr
+
+    @staticmethod
+    def InheritTypes(config):
+
+        descriptors = config.getDescriptors(register=True, hasInterfaceObject=True)
+        allprotos = [CGGeneric(declare="#[allow(unused_imports)];\n"),
+                     CGGeneric(declare="use dom::types::*;\n"),
+                     CGGeneric(declare="use dom::bindings::js::JS;\n"),
+                     CGGeneric(declare="use dom::bindings::utils::Traceable;\n"),
+                     CGGeneric(declare="use extra::serialize::{Encodable, Encoder};\n"),
+                     CGGeneric(declare="use js::jsapi::JSTracer;\n\n")]
+        for descriptor in descriptors:
+            name = descriptor.name
+            protos = [CGGeneric(declare='pub trait %s {}\n' % (name + 'Base'))]
+            for proto in descriptor.prototypeChain:
+                protos += [CGGeneric(declare='impl %s for %s {}\n' % (proto + 'Base',
+                                                                      descriptor.concreteType))]
+            derived = [CGGeneric(declare='pub trait %s { fn %s(&self) -> bool; }\n' %
+                                 (name + 'Derived', 'is_' + name.lower()))]
+            for protoName in descriptor.prototypeChain[1:-1]:
+                protoDescriptor = config.getDescriptor(protoName, False)
+                delegate = string.Template('''impl ${selfName} for ${baseName} {
+  fn ${fname}(&self) -> bool {
+    self.${parentName}.${fname}()
+  }
+}
+''').substitute({'fname': 'is_' + name.lower(),
+                 'selfName': name + 'Derived',
+                 'baseName': protoDescriptor.concreteType,
+                 'parentName': protoDescriptor.prototypeChain[-2].lower()})
+                derived += [CGGeneric(declare=delegate)]
+            derived += [CGGeneric(declare='\n')]
+
+            cast = [CGGeneric(declare=string.Template('''pub trait ${castTraitName} {
+  fn from<T: ${fromBound}>(derived: &JS<T>) -> JS<Self> {
+    unsafe { derived.clone().transmute() }
+  }
+
+  fn to<T: ${toBound}>(base: &JS<T>) -> JS<Self> {
+    assert!(base.get().${checkFn}());
+    unsafe { base.clone().transmute() }
+  }
+}
+''').substitute({'checkFn': 'is_' + name.lower(),
+                 'castTraitName': name + 'Cast',
+                 'fromBound': name + 'Base',
+                 'toBound': name + 'Derived'})),
+                    CGGeneric(declare="impl %s for %s {}\n\n" % (name + 'Cast', name))]
+
+            trace = [CGGeneric(declare=string.Template('''impl Traceable for ${name} {
+    fn trace(&self, tracer: *mut JSTracer) {
+        unsafe {
+            self.encode(&mut *tracer);
+        }
+    }
+}
+''').substitute({'name': name}))]
+
+            allprotos += protos + derived + cast + trace
+
+        curr = CGList(allprotos)
+        curr = CGWrapper(curr, pre=AUTOGENERATED_WARNING_COMMENT)
+        return curr
+
+    @staticmethod
+    def UnionTypes(config):
+
+        (includes, declarations, unions) = UnionTypes(config.getDescriptors())
+        includes.add("mozilla/dom/BindingUtils.h")
+
+        # Wrap all of that in our namespaces.
+        #curr = CGNamespace.build(['mozilla', 'dom'], unions, public=True)
+        curr = unions
+
+        curr = CGWrapper(curr, post='\n')
+
+        namespaces = []
+        stack = [CGList([])]
+        for (clazz, isStruct) in SortedTuples(declarations):
+            elements = clazz.split("::")
+            elements.pop()
+            #clazz = CGClassForwardDeclare(elements.pop(), isStruct=isStruct)
+            i = 0
+            if len(elements) > 0:
+                common = min(len(namespaces), len(elements))
+                while i < common and namespaces[i] == elements[i]:
+                    i += 1
+
+            # pop all the namespaces that should be closed
+            namespaces = namespaces[:i]
+
+            # add all the namespaces that should be opened
+            for j, namespace in enumerate(elements[i:]):
+                namespaces.append(namespace)
+                # every CGNamespace that we add holds a CGList
+                list = CGList([])
+                # add the new namespace to the list on top of the stack
+                stack[i + j].append(CGNamespace(namespace, list))
+                # set the top of the namespace stack to the list of the new
+                # namespace
+                stack[i + j + 1:] = [list]
+
+            #stack[len(elements)].append(clazz)
+
+        curr = CGList([stack[0], curr], "\n")
+
+        #curr = CGHeaders([], [], includes, [], curr)
+
+        # Add include guards.
+        #curr = CGIncludeGuard('UnionTypes', curr)
+
+        curr = CGImports([], [], ['dom::bindings::js::JS',
+                                  'dom::types::*'], [], curr)
+
+        # Add the auto-generated comment.
+        curr = CGWrapper(curr, pre=AUTOGENERATED_WARNING_COMMENT)
+
+        # Done.
+        return curr
+
+    @staticmethod
+    def UnionConversions(config):
+
+        unions = UnionConversions(config.getDescriptors())
+        curr = unions
+
+        # Wrap all of that in our namespaces.
+        #curr = CGNamespace.build(['mozilla', 'dom'], unions)
+
+        curr = CGWrapper(curr, post='\n')
+
+        #curr = CGHeaders([], [], ["nsDebug.h", "mozilla/dom/UnionTypes.h", "nsDOMQS.h"], [], curr)
+
+        # Add include guards.
+        #curr = CGIncludeGuard('UnionConversions', curr)
+
+        curr = CGImports([], [], ['dom::bindings::utils::unwrap_jsmanaged',
+                                  'dom::bindings::codegen::UnionTypes::*',
+                                  'dom::bindings::codegen::PrototypeList',
+                                  'dom::bindings::conversions::JSValConvertible',
+                                  'js::*',
+                                  'js::jsapi::*',
+                                  'js::glue::*'], [], curr)
+
+        # Add the auto-generated comment.
+        curr = CGWrapper(curr, pre=AUTOGENERATED_WARNING_COMMENT)
+
+        # Done.
+        return curr
diff --git a/src/components/script/dom/bindings/codegen/Configuration.py b/src/components/script/dom/bindings/codegen/Configuration.py
index 0c87ead0259..e28e24bbcfa 100644
--- a/src/components/script/dom/bindings/codegen/Configuration.py
+++ b/src/components/script/dom/bindings/codegen/Configuration.py
@@ -158,10 +158,9 @@ class Descriptor(DescriptorProvider):
             if self.workers:
                 nativeTypeDefault = "workers::" + ifaceName
             else:
-                nativeTypeDefault = ifaceName
+                nativeTypeDefault = 'JS<%s>' % ifaceName
 
         self.nativeType = desc.get('nativeType', nativeTypeDefault)
-        self.pointerType = desc.get('pointerType', '@mut ')
         self.concreteType = desc.get('concreteType', ifaceName)
         self.needsAbstract = desc.get('needsAbstract', [])
         self.hasInstanceInterface = desc.get('hasInstanceInterface', None)
@@ -253,7 +252,7 @@ class Descriptor(DescriptorProvider):
         self.prefable = desc.get('prefable', False)
 
         self.nativeIsISupports = not self.workers
-        self.customTrace = desc.get('customTrace', self.workers)
+        self.customTrace = desc.get('customTrace', self.workers) or 'trace'
         self.customFinalize = desc.get('customFinalize', self.workers)
         self.wrapperCache = self.workers or desc.get('wrapperCache', True)
 
diff --git a/src/components/script/dom/bindings/codegen/GlobalGen.py b/src/components/script/dom/bindings/codegen/GlobalGen.py
index 9f46c786065..bd8b3d70793 100644
--- a/src/components/script/dom/bindings/codegen/GlobalGen.py
+++ b/src/components/script/dom/bindings/codegen/GlobalGen.py
@@ -83,12 +83,14 @@ def main():
     # Generate the type list.
     generate_file(config, 'InterfaceTypes', 'declare+define')
 
+    # Generate the type list.
+    generate_file(config, 'InheritTypes', 'declare+define')
+
     # Generate the module declarations.
     generate_file(config, 'BindingDeclarations', 'declare+define')
 
-    #XXXjdm No union support yet
-    #generate_file(config, 'UnionTypes', 'declare')
-    #generate_file(config, 'UnionConversions', 'declare')
+    generate_file(config, 'UnionTypes', 'declare+define')
+    generate_file(config, 'UnionConversions', 'declare+define')
 
 if __name__ == '__main__':
     main()
diff --git a/src/components/script/dom/bindings/codegen/Makefile.in b/src/components/script/dom/bindings/codegen/Makefile.in
index 69fe4be4e9b..5fef1e77218 100644
--- a/src/components/script/dom/bindings/codegen/Makefile.in
+++ b/src/components/script/dom/bindings/codegen/Makefile.in
@@ -95,7 +95,7 @@ CSS2Properties.webidl: $(topsrcdir)/layout/style/nsCSSPropList.h \
                        $(srcdir)/GenerateCSS2PropertiesWebIDL.py \
                        $(GLOBAL_DEPS)
 	$(CPP) $(DEFINES) $(ACDEFINES) -I$(topsrcdir)/layout/style $(webidl_base)/CSS2PropertiesProps.h | \
-	  PYTHONDONTWRITEBYTECODE=1 $(PYTHON) \
+	  $(PYTHON) \
 	  $(srcdir)/GenerateCSS2PropertiesWebIDL.py $(webidl_base)/CSS2Properties.webidl.in > CSS2Properties.webidl
 
 $(webidl_files): %: $(webidl_base)/%
@@ -107,7 +107,7 @@ $(test_webidl_files): %: $(srcdir)/test/%
 $(binding_header_files): %Binding.h: $(bindinggen_dependencies) \
                                      %.webidl \
                                      $(NULL)
-	PYTHONDONTWRITEBYTECODE=1 $(PYTHON) $(topsrcdir)/config/pythonpath.py \
+	$(PYTHON) $(topsrcdir)/config/pythonpath.py \
 	  $(PLY_INCLUDE) -I$(srcdir)/parser \
 	  $(srcdir)/BindingGen.py header \
 	  $(srcdir)/Bindings.conf $*Binding \
@@ -116,7 +116,7 @@ $(binding_header_files): %Binding.h: $(bindinggen_dependencies) \
 $(binding_cpp_files): %Binding.cpp: $(bindinggen_dependencies) \
                                     %.webidl \
                                     $(NULL)
-	PYTHONDONTWRITEBYTECODE=1 $(PYTHON) $(topsrcdir)/config/pythonpath.py \
+	$(PYTHON) $(topsrcdir)/config/pythonpath.py \
 	  $(PLY_INCLUDE) -I$(srcdir)/parser \
 	  $(srcdir)/BindingGen.py cpp \
 	  $(srcdir)/Bindings.conf $*Binding \
@@ -142,7 +142,7 @@ $(CACHE_DIR)/.done:
 
 ParserResults.pkl: $(globalgen_dependencies) \
                    $(all_webidl_files)
-	PYTHONDONTWRITEBYTECODE=1 $(PYTHON) $(topsrcdir)/config/pythonpath.py \
+	$(PYTHON) $(topsrcdir)/config/pythonpath.py \
     $(PLY_INCLUDE) -I$(srcdir)/parser \
     $(srcdir)/GlobalGen.py $(srcdir)/Bindings.conf . \
     --cachedir=$(CACHE_DIR) \
diff --git a/src/components/script/dom/bindings/codegen/test/Makefile.in b/src/components/script/dom/bindings/codegen/test/Makefile.in
index de388187c87..d8104db5ffd 100644
--- a/src/components/script/dom/bindings/codegen/test/Makefile.in
+++ b/src/components/script/dom/bindings/codegen/test/Makefile.in
@@ -79,9 +79,9 @@ $(CPPSRCS): ../%Binding.cpp: $(bindinggen_dependencies) \
 	$(MAKE) -C .. $*Binding.cpp
 
 check::
-	PYTHONDONTWRITEBYTECODE=1 $(PYTHON) $(topsrcdir)/config/pythonpath.py \
+	$(PYTHON) $(topsrcdir)/config/pythonpath.py \
 	  $(PLY_INCLUDE) $(srcdir)/../parser/runtests.py
 
 check-interactive:
-	PYTHONDONTWRITEBYTECODE=1 $(PYTHON) $(topsrcdir)/config/pythonpath.py \
+	$(PYTHON) $(topsrcdir)/config/pythonpath.py \
 	  $(PLY_INCLUDE) $(srcdir)/../parser/runtests.py -q
diff --git a/src/components/script/dom/bindings/conversions.rs b/src/components/script/dom/bindings/conversions.rs
index 06745217365..decb047ab9f 100644
--- a/src/components/script/dom/bindings/conversions.rs
+++ b/src/components/script/dom/bindings/conversions.rs
@@ -4,7 +4,9 @@
 
 use js::jsapi::JSVal;
 use js::{JSVAL_FALSE, JSVAL_TRUE};
-use js::glue::{RUST_UINT_TO_JSVAL, RUST_JSVAL_TO_INT, RUST_DOUBLE_TO_JSVAL, RUST_JSVAL_TO_DOUBLE};
+use js::glue::{RUST_UINT_TO_JSVAL, RUST_JSVAL_TO_INT, RUST_DOUBLE_TO_JSVAL};
+use js::glue::{RUST_JSVAL_TO_DOUBLE, RUST_JSVAL_IS_INT, RUST_JSVAL_IS_DOUBLE};
+use js::glue::{RUST_JSVAL_IS_BOOLEAN, RUST_JSVAL_TO_BOOLEAN};
 
 pub trait JSValConvertible {
     fn to_jsval(&self) -> JSVal;
@@ -21,7 +23,11 @@ impl JSValConvertible for i64 {
 
     fn from_jsval(val: JSVal) -> Option<i64> {
         unsafe {
-            Some(RUST_JSVAL_TO_DOUBLE(val) as i64)
+            if RUST_JSVAL_IS_INT(val) != 0 {
+                Some(RUST_JSVAL_TO_DOUBLE(val) as i64)
+            } else {
+                None
+            }
         }
     }
 }
@@ -35,7 +41,11 @@ impl JSValConvertible for u32 {
 
     fn from_jsval(val: JSVal) -> Option<u32> {
         unsafe {
-            Some(RUST_JSVAL_TO_INT(val) as u32)
+            if RUST_JSVAL_IS_INT(val) != 0 {
+                Some(RUST_JSVAL_TO_INT(val) as u32)
+            } else {
+                None
+            }
         }
     }
 }
@@ -49,7 +59,11 @@ impl JSValConvertible for i32 {
 
     fn from_jsval(val: JSVal) -> Option<i32> {
         unsafe {
-            Some(RUST_JSVAL_TO_INT(val) as i32)
+            if RUST_JSVAL_IS_INT(val) != 0 {
+                Some(RUST_JSVAL_TO_INT(val) as i32)
+            } else {
+                None
+            }
         }
     }
 }
@@ -63,7 +77,11 @@ impl JSValConvertible for u16 {
 
     fn from_jsval(val: JSVal) -> Option<u16> {
         unsafe {
-            Some(RUST_JSVAL_TO_INT(val) as u16)
+            if RUST_JSVAL_IS_INT(val) != 0 {
+                Some(RUST_JSVAL_TO_INT(val) as u16)
+            } else {
+                None
+            }
         }
     }
 }
@@ -78,12 +96,12 @@ impl JSValConvertible for bool {
     }
 
     fn from_jsval(val: JSVal) -> Option<bool> {
-        if val == JSVAL_TRUE {
-            Some(true)
-        } else if val == JSVAL_FALSE {
-            Some(false)
-        } else {
-            None
+        unsafe {
+            if RUST_JSVAL_IS_BOOLEAN(val) != 0 {
+                Some(RUST_JSVAL_TO_BOOLEAN(val) != 0)
+            } else {
+                None
+            }
         }
     }
 }
@@ -97,7 +115,11 @@ impl JSValConvertible for f32 {
 
     fn from_jsval(val: JSVal) -> Option<f32> {
         unsafe {
-            Some(RUST_JSVAL_TO_DOUBLE(val) as f32)
+            if RUST_JSVAL_IS_DOUBLE(val) != 0 {
+                Some(RUST_JSVAL_TO_DOUBLE(val) as f32)
+            } else {
+                None
+            }
         }
     }
 }
@@ -111,7 +133,11 @@ impl JSValConvertible for f64 {
 
     fn from_jsval(val: JSVal) -> Option<f64> {
         unsafe {
-            Some(RUST_JSVAL_TO_DOUBLE(val) as f64)
+            if RUST_JSVAL_IS_DOUBLE(val) != 0 {
+                Some(RUST_JSVAL_TO_DOUBLE(val) as f64)
+            } else {
+                None
+            }
         }
     }
 }
diff --git a/src/components/script/dom/bindings/element.rs b/src/components/script/dom/bindings/element.rs
index 9bbaf08fc6e..64190409ef5 100644
--- a/src/components/script/dom/bindings/element.rs
+++ b/src/components/script/dom/bindings/element.rs
@@ -3,9 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::types::*;
-use dom::bindings::utils::{Reflectable, Reflector, Traceable};
-
-use js::jsapi::JSTracer;
+use dom::bindings::utils::{Reflectable, Reflector};
 
 // generate_cacheable_wrapper
 macro_rules! generate_cacheable_wrapper(
@@ -58,277 +56,149 @@ macro_rules! generate_cacheable_wrapper_base(
     )
 )
 
-
-// generate_traceable
-macro_rules! generate_traceable(
-    ($name: path) => (
-        generate_traceable_base!($name, element)
-    )
-)
-
-macro_rules! generate_traceable_characterdata(
-    ($name: path) => (
-        generate_traceable_base!($name, characterdata)
-    )
-)
-
-macro_rules! generate_traceable_htmlelement(
-    ($name: path) => (
-        generate_traceable_base!($name, htmlelement)
-    )
-)
-
-macro_rules! generate_traceable_htmlmediaelement(
-    ($name: path) => (
-        generate_traceable_base!($name, htmlmediaelement)
-    )
-)
-
-macro_rules! generate_traceable_htmltablecellelement(
-    ($name: path) => (
-        generate_traceable_base!($name, htmltablecellelement)
-    )
-)
-
-macro_rules! generate_traceable_node(
-    ($name: path) => (
-        generate_traceable_base!($name, node)
-    )
-)
-
-macro_rules! generate_traceable_base(
-    ($name: path, $parent: ident) => (
-        impl Traceable for $name {
-            fn trace(&self, trc: *mut JSTracer) {
-                self.$parent.trace(trc);
-            }
-        }
-    )
-)
-
-
 generate_cacheable_wrapper_characterdata!(Comment, CommentBinding::Wrap)
-generate_traceable_characterdata!(Comment)
 
 generate_cacheable_wrapper_node!(DocumentFragment, DocumentFragmentBinding::Wrap)
-generate_traceable_node!(DocumentFragment)
 
 generate_cacheable_wrapper_node!(DocumentType, DocumentTypeBinding::Wrap)
-generate_traceable_node!(DocumentType)
 
 generate_cacheable_wrapper_characterdata!(Text, TextBinding::Wrap)
-generate_traceable_characterdata!(Text)
 
 generate_cacheable_wrapper_characterdata!(ProcessingInstruction, ProcessingInstruction::Wrap)
-generate_traceable_characterdata!(ProcessingInstruction)
 
 generate_cacheable_wrapper_htmlelement!(HTMLHeadElement, HTMLHeadElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLHeadElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLAnchorElement, HTMLAnchorElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLAnchorElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLAppletElement, HTMLAppletElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLAppletElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLAreaElement, HTMLAreaElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLAreaElement)
 
 generate_cacheable_wrapper_htmlmediaelement!(HTMLAudioElement, HTMLAudioElementBinding::Wrap)
-generate_traceable_htmlmediaelement!(HTMLAudioElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLBaseElement, HTMLBaseElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLBaseElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLBodyElement, HTMLBodyElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLBodyElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLButtonElement, HTMLButtonElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLButtonElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLCanvasElement, HTMLCanvasElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLCanvasElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLDataListElement, HTMLDataListElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLDataListElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLDListElement, HTMLDListElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLDListElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLFormElement, HTMLFormElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLFormElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLFrameElement, HTMLFrameElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLFrameElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLFrameSetElement, HTMLFrameSetElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLFrameSetElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLBRElement, HTMLBRElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLBRElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLHRElement, HTMLHRElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLHRElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLHtmlElement, HTMLHtmlElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLHtmlElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLDataElement, HTMLDataElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLDataElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLDirectoryElement, HTMLDirectoryElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLDirectoryElement)
-
 generate_cacheable_wrapper_htmlelement!(HTMLDivElement, HTMLDivElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLDivElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLEmbedElement, HTMLEmbedElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLEmbedElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLFieldSetElement, HTMLFieldSetElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLFieldSetElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLFontElement, HTMLFontElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLFontElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLHeadingElement, HTMLHeadingElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLHeadingElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLIFrameElement, HTMLIFrameElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLIFrameElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLImageElement, HTMLImageElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLImageElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLInputElement, HTMLInputElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLInputElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLLabelElement, HTMLLabelElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLLabelElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLLegendElement, HTMLLegendElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLLegendElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLLIElement, HTMLLIElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLLIElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLLinkElement, HTMLLinkElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLLinkElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLMainElement, HTMLMainElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLMainElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLMapElement, HTMLMapElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLMapElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLMediaElement, HTMLMediaElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLMediaElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLMetaElement, HTMLMetaElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLMetaElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLMeterElement, HTMLMeterElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLMeterElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLModElement, HTMLModElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLModElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLObjectElement, HTMLObjectElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLObjectElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLOListElement, HTMLOListElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLOListElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLOptGroupElement, HTMLOptGroupElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLOptGroupElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLOptionElement, HTMLOptionElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLOptionElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLOutputElement, HTMLOutputElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLOutputElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLParagraphElement, HTMLParagraphElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLParagraphElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLParamElement, HTMLParamElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLParamElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLPreElement, HTMLPreElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLPreElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLProgressElement, HTMLProgressElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLProgressElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLQuoteElement, HTMLQuoteElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLQuoteElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLScriptElement, HTMLScriptElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLScriptElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLSelectElement, HTMLSelectElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLSelectElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLSourceElement, HTMLSourceElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLSourceElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLSpanElement, HTMLSpanElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLSpanElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLStyleElement, HTMLStyleElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLStyleElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTableElement, HTMLTableElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTableElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTableCaptionElement, HTMLTableCaptionElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTableCaptionElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTableCellElement, HTMLTableCellElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTableCellElement)
 
 generate_cacheable_wrapper_htmltablecellelement!(HTMLTableDataCellElement, HTMLTableDataCellElementBinding::Wrap)
-generate_traceable_htmltablecellelement!(HTMLTableDataCellElement)
 
 generate_cacheable_wrapper_htmltablecellelement!(HTMLTableHeaderCellElement, HTMLTableHeaderCellElementBinding::Wrap)
-generate_traceable_htmltablecellelement!(HTMLTableHeaderCellElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTableColElement, HTMLTableColElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTableColElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTableRowElement, HTMLTableRowElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTableRowElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTableSectionElement, HTMLTableSectionElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTableSectionElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTemplateElement, HTMLTemplateElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTemplateElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTextAreaElement, HTMLTextAreaElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTextAreaElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTitleElement, HTMLTitleElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTitleElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTimeElement, HTMLTimeElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTimeElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLTrackElement, HTMLTrackElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLTrackElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLUListElement, HTMLUListElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLUListElement)
 
 generate_cacheable_wrapper_htmlelement!(HTMLUnknownElement, HTMLUnknownElementBinding::Wrap)
-generate_traceable_htmlelement!(HTMLUnknownElement)
 
 generate_cacheable_wrapper_htmlmediaelement!(HTMLVideoElement, HTMLVideoElementBinding::Wrap)
-generate_traceable_htmlmediaelement!(HTMLVideoElement)
 
 generate_cacheable_wrapper!(HTMLElement, HTMLElementBinding::Wrap)
-generate_traceable!(HTMLElement)
-
-generate_traceable_node!(Element)
-
-generate_traceable_node!(CharacterData)
diff --git a/src/components/script/dom/bindings/js.rs b/src/components/script/dom/bindings/js.rs
new file mode 100644
index 00000000000..aa7ba954a48
--- /dev/null
+++ b/src/components/script/dom/bindings/js.rs
@@ -0,0 +1,99 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::utils::{Reflector, Reflectable};
+use dom::window;
+use js::jsapi::{JSContext, JSObject};
+use layout_interface::TrustedNodeAddress;
+
+use std::cast;
+use std::cell::RefCell;
+use std::unstable::raw::Box;
+
+pub struct JS<T> {
+    priv ptr: RefCell<*mut T>
+}
+
+impl<T> Eq for JS<T> {
+    fn eq(&self, other: &JS<T>) -> bool {
+        self.ptr == other.ptr
+    }
+}
+
+impl <T> Clone for JS<T> {
+    fn clone(&self) -> JS<T> {
+        JS {
+            ptr: self.ptr.clone()
+        }
+    }
+}
+
+impl<T: Reflectable> JS<T> {
+    pub fn new(mut obj: ~T,
+               window:  &window::Window,
+               wrap_fn: extern "Rust" fn(*JSContext, *JSObject, ~T) -> *JSObject) -> JS<T> {
+        let cx = window.get_cx();
+        let scope = window.reflector().get_jsobject();
+        let raw: *mut T = &mut *obj;
+        if wrap_fn(cx, scope, obj).is_null() {
+            fail!("Could not eagerly wrap object");
+        }
+        JS {
+            ptr: RefCell::new(raw)
+        }
+    }
+
+    pub unsafe fn from_raw(raw: *mut T) -> JS<T> {
+        JS {
+            ptr: RefCell::new(raw)
+        }
+    }
+
+
+    pub unsafe fn from_box(box_: *mut Box<T>) -> JS<T> {
+        let raw: *mut T = &mut (*box_).data;
+        JS {
+            ptr: RefCell::new(raw)
+        }
+    }
+
+    pub unsafe fn from_trusted_node_address(inner: TrustedNodeAddress) -> JS<T> {
+        JS {
+            ptr: RefCell::new(inner as *mut T)
+        }
+    }
+}
+
+impl<T: Reflectable> Reflectable for JS<T> {
+    fn reflector<'a>(&'a self) -> &'a Reflector {
+        self.get().reflector()
+    }
+
+    fn mut_reflector<'a>(&'a mut self) -> &'a mut Reflector {
+        self.get_mut().mut_reflector()
+    }
+}
+
+impl<T> JS<T> {
+    pub fn get<'a>(&'a self) -> &'a T {
+        let borrowed = self.ptr.borrow();
+        unsafe {
+            &(**borrowed.get())
+        }
+    }
+
+    pub fn get_mut<'a>(&'a mut self) -> &'a mut T {
+        let mut borrowed = self.ptr.borrow_mut();
+        unsafe {
+            &mut (**borrowed.get())
+        }
+    }
+}
+
+impl<From, To> JS<From> {
+    //XXXjdm It would be lovely if this could be private.
+    pub unsafe fn transmute(self) -> JS<To> {
+        cast::transmute(self)
+    }
+}
diff --git a/src/components/script/dom/bindings/node.rs b/src/components/script/dom/bindings/node.rs
deleted file mode 100644
index 8bf2ab8a565..00000000000
--- a/src/components/script/dom/bindings/node.rs
+++ /dev/null
@@ -1,52 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-use dom::bindings::utils::{Reflectable, Reflector, Traceable, trace_reflector};
-use dom::types::*;
-use dom::node::AbstractNode;
-
-use std::cast;
-use std::libc;
-use std::ptr;
-use js::jsapi::{JSTracer, JSTRACE_OBJECT, JS_CallTracer};
-
-impl Reflectable for AbstractNode {
-    fn reflector<'a>(&'a self) -> &'a Reflector {
-        self.node().reflector()
-    }
-
-    fn mut_reflector<'a>(&'a mut self) -> &'a mut Reflector {
-        self.mut_node().mut_reflector()
-    }
-}
-
-impl Traceable for Node {
-    fn trace(&self, tracer: *mut JSTracer) {
-        fn trace_node(tracer: *mut JSTracer, node: Option<AbstractNode>, name: &str) {
-            if node.is_none() {
-                return;
-            }
-            debug!("tracing {:s}", name);
-            let node = node.unwrap();
-            let obj = node.reflector().get_jsobject();
-            assert!(obj.is_not_null());
-            unsafe {
-                (*tracer).debugPrinter = ptr::null();
-                (*tracer).debugPrintIndex = -1;
-                name.to_c_str().with_ref(|name| {
-                    (*tracer).debugPrintArg = name as *libc::c_void;
-                    JS_CallTracer(cast::transmute(tracer), obj, JSTRACE_OBJECT as u32);
-                });
-            }
-        }
-        debug!("tracing {:p}?:", self.reflector().get_jsobject());
-        trace_node(tracer, self.parent_node, "parent");
-        trace_node(tracer, self.first_child, "first child");
-        trace_node(tracer, self.last_child, "last child");
-        trace_node(tracer, self.next_sibling, "next sibling");
-        trace_node(tracer, self.prev_sibling, "prev sibling");
-        let owner_doc = self.owner_doc();
-        trace_reflector(tracer, "document", owner_doc.reflector());
-    }
-}
diff --git a/src/components/script/dom/bindings/trace.rs b/src/components/script/dom/bindings/trace.rs
new file mode 100644
index 00000000000..6565bf8c2d9
--- /dev/null
+++ b/src/components/script/dom/bindings/trace.rs
@@ -0,0 +1,28 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use dom::bindings::js::JS;
+use dom::bindings::utils::{Reflectable, trace_reflector, Reflector};
+
+use js::jsapi::JSTracer;
+
+use std::cast;
+use extra::serialize::{Encodable, Encoder};
+
+// IMPORTANT: We rely on the fact that we never attempt to encode DOM objects using
+//            any encoder but JSTracer. Since we derive trace hooks automatically,
+//            we are unfortunately required to use generic types everywhere and
+//            unsafely cast to the concrete JSTracer we actually require.
+
+impl<T: Reflectable+Encodable<S>, S: Encoder> Encodable<S> for JS<T> {
+    fn encode(&self, s: &mut S) {
+        let s: &mut JSTracer = unsafe { cast::transmute(s) };
+        trace_reflector(s, "", self.reflector());
+    }
+}
+
+impl<S: Encoder> Encodable<S> for Reflector {
+    fn encode(&self, _s: &mut S) {
+    }
+}
diff --git a/src/components/script/dom/bindings/utils.rs b/src/components/script/dom/bindings/utils.rs
index 671f92e3766..80787d93416 100644
--- a/src/components/script/dom/bindings/utils.rs
+++ b/src/components/script/dom/bindings/utils.rs
@@ -4,11 +4,13 @@
 
 use dom::bindings::codegen::PrototypeList;
 use dom::bindings::codegen::PrototypeList::MAX_PROTO_CHAIN_LENGTH;
+use dom::bindings::js::JS;
 use dom::window;
 use servo_util::str::DOMString;
 
 use std::libc::c_uint;
 use std::cast;
+use std::cmp::Eq;
 use std::hashmap::HashMap;
 use std::libc;
 use std::ptr;
@@ -32,7 +34,7 @@ use js::jsapi::{JSContext, JSObject, JSBool, jsid, JSClass, JSNative, JSTracer};
 use js::jsapi::{JSFunctionSpec, JSPropertySpec, JSVal, JSPropertyDescriptor};
 use js::jsapi::{JS_NewGlobalObject, JS_InitStandardClasses};
 use js::jsapi::{JSString, JS_CallTracer, JSTRACE_OBJECT};
-use js::jsapi::{JS_IsExceptionPending};
+use js::jsapi::{JS_IsExceptionPending, JS_AllowGC, JS_InhibitGC};
 use js::jsfriendapi::bindgen::JS_NewObjectWithUniqueType;
 use js::{JSPROP_ENUMERATE, JSVAL_NULL, JSCLASS_IS_GLOBAL, JSCLASS_IS_DOMJSCLASS};
 use js::{JSPROP_PERMANENT, JSID_VOID, JSPROP_NATIVE_ACCESSORS, JSPROP_GETTER};
@@ -174,6 +176,17 @@ pub fn unwrap_object<T>(obj: *JSObject, proto_id: PrototypeList::id::ID, proto_d
     }
 }
 
+pub fn unwrap_jsmanaged<T: Reflectable>(obj: *JSObject,
+                                        proto_id: PrototypeList::id::ID,
+                                        proto_depth: uint) -> Result<JS<T>, ()> {
+    let result: Result<*mut Box<T>, ()> = unwrap_object(obj, proto_id, proto_depth);
+    result.map(|unwrapped| {
+        unsafe {
+            JS::from_box(unwrapped)
+        }
+    })
+}
+
 pub fn unwrap_value<T>(val: *JSVal, proto_id: PrototypeList::id::ID, proto_depth: uint) -> Result<T, ()> {
     unsafe {
         let obj = RUST_JSVAL_TO_OBJECT(*val);
@@ -182,8 +195,11 @@ pub fn unwrap_value<T>(val: *JSVal, proto_id: PrototypeList::id::ID, proto_depth
 }
 
 pub unsafe fn squirrel_away<T>(x: @mut T) -> *Box<T> {
-    let y: *Box<T> = cast::transmute(x);
-    y
+    cast::transmute(x)
+}
+
+pub unsafe fn squirrel_away_unique<T>(x: ~T) -> *Box<T> {
+    cast::transmute(x)
 }
 
 pub fn jsstring_to_str(cx: *JSContext, s: *JSString) -> DOMString {
@@ -557,10 +573,6 @@ pub fn trace_reflector(tracer: *mut JSTracer, description: &str, reflector: &Ref
     }
 }
 
-pub fn trace_option<T: Reflectable>(tracer: *mut JSTracer, description: &str, option: Option<@mut T>) {
-    option.map(|some| trace_reflector(tracer, description, some.reflector()));
-}
-
 pub fn initialize_global(global: *JSObject) {
     let protoArray = @mut ([0 as *JSObject, ..PrototypeList::id::_ID_Count as uint]);
     unsafe {
@@ -579,21 +591,17 @@ pub trait Reflectable {
 }
 
 pub fn reflect_dom_object<T: Reflectable>
-        (obj:     @mut T,
+        (obj:     ~T,
          window:  &window::Window,
-         wrap_fn: extern "Rust" fn(*JSContext, *JSObject, @mut T) -> *JSObject)
-         ->       @mut T {
-    let cx = window.get_cx();
-    let scope = window.reflector().get_jsobject();
-    if wrap_fn(cx, scope, obj).is_null() {
-        fail!("Could not eagerly wrap object");
-    }
-    assert!(obj.reflector().get_jsobject().is_not_null());
-    obj
+         wrap_fn: extern "Rust" fn(*JSContext, *JSObject, ~T) -> *JSObject)
+         ->       JS<T> {
+    JS::new(obj, window, wrap_fn)
 }
 
+#[deriving(Eq)]
 pub struct Reflector {
-    object: *JSObject
+    object: *JSObject,
+    force_box_layout: @int,
 }
 
 impl Reflector {
@@ -610,7 +618,8 @@ impl Reflector {
 
     pub fn new() -> Reflector {
         Reflector {
-            object: ptr::null()
+            object: ptr::null(),
+            force_box_layout: @1,
         }
     }
 }
@@ -849,11 +858,11 @@ fn cx_for_dom_reflector(obj: *JSObject) -> *JSContext {
 }
 
 /// Returns the global object of the realm that the given DOM object was created in.
-pub fn global_object_for_dom_object<T: Reflectable>(obj: &mut T) -> *Box<window::Window> {
+pub fn global_object_for_dom_object<T: Reflectable>(obj: &T) -> *Box<window::Window> {
     global_object_for_js_object(obj.reflector().get_jsobject())
 }
 
-pub fn cx_for_dom_object<T: Reflectable>(obj: &mut T) -> *JSContext {
+pub fn cx_for_dom_object<T: Reflectable>(obj: &T) -> *JSContext {
     cx_for_dom_reflector(obj.reflector().get_jsobject())
 }
 
@@ -870,6 +879,35 @@ pub fn throw_method_failed_with_details<T>(cx: *JSContext,
     return 0;
 }
 
+pub fn throw_not_in_union(cx: *JSContext, names: &'static str) -> JSBool {
+    assert!(unsafe { JS_IsExceptionPending(cx) } == 0);
+    let message = format!("argument could not be converted to any of: {}", names);
+    message.with_c_str(|string| {
+        unsafe { ReportError(cx, string) };
+    });
+    return 0;
+}
+
+/// Execute arbitrary code with the JS GC enabled, then disable it afterwards.
+pub fn with_gc_enabled<R>(cx: *JSContext, f: || -> R) -> R {
+    unsafe {
+        JS_AllowGC(cx);
+        let rv = f();
+        JS_InhibitGC(cx);
+        rv
+    }
+}
+
+/// Execute arbitrary code with the JS GC disabled, then enable it afterwards.
+pub fn with_gc_disabled<R>(cx: *JSContext, f: || -> R) -> R {
+    unsafe {
+        JS_InhibitGC(cx);
+        let rv = f();
+        JS_AllowGC(cx);
+        rv
+    }
+}
+
 /// Check if an element name is valid. See http://www.w3.org/TR/xml/#NT-Name
 /// for details.
 #[deriving(Eq)]
diff --git a/src/components/script/dom/blob.rs b/src/components/script/dom/blob.rs
index 2bf0d0b7510..386b9447590 100644
--- a/src/components/script/dom/blob.rs
+++ b/src/components/script/dom/blob.rs
@@ -2,32 +2,36 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::utils::Fallible;
 use dom::bindings::codegen::BlobBinding;
 use dom::window::Window;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct Blob {
     reflector_: Reflector,
-    window: @mut Window,
+    window: JS<Window>
 }
 
 impl Blob {
-    pub fn new_inherited(window: @mut Window) -> Blob {
+    pub fn new_inherited(window: JS<Window>) -> Blob {
         Blob {
             reflector_: Reflector::new(),
-            window: window,
+            window: window
         }
     }
 
-    pub fn new(window: @mut Window) -> @mut Blob {
-        reflect_dom_object(@mut Blob::new_inherited(window), window, BlobBinding::Wrap)
+    pub fn new(window: &JS<Window>) -> JS<Blob> {
+        reflect_dom_object(~Blob::new_inherited(window.clone()),
+                           window.get(),
+                           BlobBinding::Wrap)
     }
 }
 
 impl Blob {
-    pub fn Constructor(window: @mut Window) -> Fallible<@mut Blob> {
+    pub fn Constructor(window: &JS<Window>) -> Fallible<JS<Blob>> {
         Ok(Blob::new(window))
     }
 
@@ -39,8 +43,8 @@ impl Blob {
         ~""
     }
 
-    pub fn Slice(&self, _start: i64, _end: i64, _contentType: Option<DOMString>) -> @mut Blob {
-        Blob::new(self.window)
+    pub fn Slice(&self, _start: i64, _end: i64, _contentType: Option<DOMString>) -> JS<Blob> {
+        Blob::new(&self.window)
     }
 
     pub fn Close(&self) {}
diff --git a/src/components/script/dom/characterdata.rs b/src/components/script/dom/characterdata.rs
index 0ad5f35bc78..f4bb567b5c6 100644
--- a/src/components/script/dom/characterdata.rs
+++ b/src/components/script/dom/characterdata.rs
@@ -4,19 +4,34 @@
 
 //! DOM bindings for `CharacterData`.
 
+use dom::bindings::codegen::InheritTypes::CharacterDataDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Fallible, ErrorResult};
 use dom::bindings::utils::{Reflectable, Reflector};
-use dom::document::AbstractDocument;
-use dom::node::{Node, NodeTypeId};
+use dom::document::Document;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::node::{CommentNodeTypeId, Node, NodeTypeId, TextNodeTypeId, ProcessingInstructionNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct CharacterData {
     node: Node,
     data: DOMString,
 }
 
+impl CharacterDataDerived for EventTarget {
+    fn is_characterdata(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(TextNodeTypeId) |
+            NodeTargetTypeId(CommentNodeTypeId) |
+            NodeTargetTypeId(ProcessingInstructionNodeTypeId) => true,
+            _ => false
+        }
+    }
+}
+
 impl CharacterData {
-    pub fn new_inherited(id: NodeTypeId, data: DOMString, document: AbstractDocument) -> CharacterData {
+    pub fn new_inherited(id: NodeTypeId, data: DOMString, document: JS<Document>) -> CharacterData {
         CharacterData {
             node: Node::new_inherited(id, document),
             data: data
diff --git a/src/components/script/dom/clientrect.rs b/src/components/script/dom/clientrect.rs
index 366c33fecbe..e4fd8716c26 100644
--- a/src/components/script/dom/clientrect.rs
+++ b/src/components/script/dom/clientrect.rs
@@ -3,21 +3,23 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::ClientRectBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::window::Window;
 use servo_util::geometry::Au;
 
+#[deriving(Encodable)]
 pub struct ClientRect {
     reflector_: Reflector,
     top: f32,
     bottom: f32,
     left: f32,
     right: f32,
-    window: @mut Window,
+    window: JS<Window>,
 }
 
 impl ClientRect {
-    pub fn new_inherited(window: @mut Window,
+    pub fn new_inherited(window: JS<Window>,
                          top: Au, bottom: Au,
                          left: Au, right: Au) -> ClientRect {
         ClientRect {
@@ -30,11 +32,11 @@ impl ClientRect {
         }
     }
 
-    pub fn new(window: @mut Window,
+    pub fn new(window: &JS<Window>,
                top: Au, bottom: Au,
-               left: Au, right: Au) -> @mut ClientRect {
-        let rect = ClientRect::new_inherited(window, top, bottom, left, right);
-        reflect_dom_object(@mut rect, window, ClientRectBinding::Wrap)
+               left: Au, right: Au) -> JS<ClientRect> {
+        let rect = ClientRect::new_inherited(window.clone(), top, bottom, left, right);
+        reflect_dom_object(~rect, window.get(), ClientRectBinding::Wrap)
     }
 
 
diff --git a/src/components/script/dom/clientrectlist.rs b/src/components/script/dom/clientrectlist.rs
index 7d221754fa3..bae001379ae 100644
--- a/src/components/script/dom/clientrectlist.rs
+++ b/src/components/script/dom/clientrectlist.rs
@@ -3,19 +3,21 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::ClientRectListBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::clientrect::ClientRect;
 use dom::window::Window;
 
+#[deriving(Encodable)]
 pub struct ClientRectList {
     reflector_: Reflector,
-    rects: ~[@mut ClientRect],
-    window: @mut Window,
+    rects: ~[JS<ClientRect>],
+    window: JS<Window>,
 }
 
 impl ClientRectList {
-    pub fn new_inherited(window: @mut Window,
-                         rects: ~[@mut ClientRect]) -> ClientRectList {
+    pub fn new_inherited(window: JS<Window>,
+                         rects: ~[JS<ClientRect>]) -> ClientRectList {
         ClientRectList {
             reflector_: Reflector::new(),
             rects: rects,
@@ -23,25 +25,25 @@ impl ClientRectList {
         }
     }
 
-    pub fn new(window: @mut Window,
-               rects: ~[@mut ClientRect]) -> @mut ClientRectList {
-        reflect_dom_object(@mut ClientRectList::new_inherited(window, rects),
-                           window, ClientRectListBinding::Wrap)
+    pub fn new(window: &JS<Window>,
+               rects: ~[JS<ClientRect>]) -> JS<ClientRectList> {
+        reflect_dom_object(~ClientRectList::new_inherited(window.clone(), rects),
+                           window.get(), ClientRectListBinding::Wrap)
     }
 
     pub fn Length(&self) -> u32 {
         self.rects.len() as u32
     }
 
-    pub fn Item(&self, index: u32) -> Option<@mut ClientRect> {
+    pub fn Item(&self, index: u32) -> Option<JS<ClientRect>> {
         if index < self.rects.len() as u32 {
-            Some(self.rects[index])
+            Some(self.rects[index].clone())
         } else {
             None
         }
     }
 
-    pub fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<@mut ClientRect> {
+    pub fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<JS<ClientRect>> {
         *found = index < self.rects.len() as u32;
         self.Item(index)
     }
diff --git a/src/components/script/dom/comment.rs b/src/components/script/dom/comment.rs
index a94c7bb2970..5dcfde7b418 100644
--- a/src/components/script/dom/comment.rs
+++ b/src/components/script/dom/comment.rs
@@ -2,32 +2,45 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::codegen::InheritTypes::CommentDerived;
 use dom::bindings::codegen::CommentBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::Fallible;
 use dom::characterdata::CharacterData;
-use dom::document::AbstractDocument;
-use dom::node::{AbstractNode, CommentNodeTypeId, Node};
+use dom::document::Document;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::node::{CommentNodeTypeId, Node};
 use dom::window::Window;
 use servo_util::str::DOMString;
 
 /// An HTML comment.
+#[deriving(Encodable)]
 pub struct Comment {
     characterdata: CharacterData,
 }
 
+impl CommentDerived for EventTarget {
+    fn is_comment(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(CommentNodeTypeId) => true,
+            _ => false
+        }
+    }
+}
+
 impl Comment {
-    pub fn new_inherited(text: DOMString, document: AbstractDocument) -> Comment {
+    pub fn new_inherited(text: DOMString, document: JS<Document>) -> Comment {
         Comment {
             characterdata: CharacterData::new_inherited(CommentNodeTypeId, text, document)
         }
     }
 
-    pub fn new(text: DOMString, document: AbstractDocument) -> AbstractNode {
-        let node = Comment::new_inherited(text, document);
-        Node::reflect_node(@mut node, document, CommentBinding::Wrap)
+    pub fn new(text: DOMString, document: &JS<Document>) -> JS<Comment> {
+        let node = Comment::new_inherited(text, document.clone());
+        Node::reflect_node(~node, document, CommentBinding::Wrap)
     }
 
-    pub fn Constructor(owner: @mut Window, data: DOMString) -> Fallible<AbstractNode> {
-        Ok(Comment::new(data, owner.Document()))
+    pub fn Constructor(owner: &JS<Window>, data: DOMString) -> Fallible<JS<Comment>> {
+        Ok(Comment::new(data, &owner.get().Document()))
     }
 }
diff --git a/src/components/script/dom/console.rs b/src/components/script/dom/console.rs
index 98d12a17389..3c5a219b39c 100644
--- a/src/components/script/dom/console.rs
+++ b/src/components/script/dom/console.rs
@@ -2,11 +2,13 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::codegen::ConsoleBinding;
+use dom::bindings::js::JS;
+use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::window::Window;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct Console {
     reflector_: Reflector
 }
@@ -18,8 +20,8 @@ impl Console {
         }
     }
 
-    pub fn new(window: &Window) -> @mut Console {
-        reflect_dom_object(@mut Console::new_inherited(), window, ConsoleBinding::Wrap)
+    pub fn new(window: &Window) -> JS<Console> {
+        reflect_dom_object(~Console::new_inherited(), window, ConsoleBinding::Wrap)
     }
 
     pub fn Log(&self, message: DOMString) {
diff --git a/src/components/script/dom/document.rs b/src/components/script/dom/document.rs
index 37df96353a9..e839e4aa233 100644
--- a/src/components/script/dom/document.rs
+++ b/src/components/script/dom/document.rs
@@ -2,25 +2,35 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use dom::comment::Comment;
+use dom::bindings::codegen::InheritTypes::{DocumentDerived, EventCast, HTMLElementCast};
+use dom::bindings::codegen::InheritTypes::{DocumentBase, NodeCast, DocumentCast};
+use dom::bindings::codegen::InheritTypes::{HTMLHeadElementCast, TextCast, ElementCast};
+use dom::bindings::codegen::InheritTypes::{DocumentTypeCast, HTMLHtmlElementCast};
 use dom::bindings::codegen::DocumentBinding;
-use dom::bindings::utils::{Reflectable, Reflector, Traceable, reflect_dom_object};
+use dom::bindings::js::JS;
+use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::utils::{ErrorResult, Fallible, NotSupported, InvalidCharacter, HierarchyRequest};
 use dom::bindings::utils::{xml_name_type, InvalidXMLName};
+use dom::comment::Comment;
 use dom::documentfragment::DocumentFragment;
+use dom::documenttype::DocumentType;
 use dom::domimplementation::DOMImplementation;
 use dom::element::{Element};
-use dom::element::{HTMLHtmlElementTypeId, HTMLHeadElementTypeId, HTMLTitleElementTypeId, HTMLBodyElementTypeId, HTMLFrameSetElementTypeId};
-use dom::event::{AbstractEvent, Event};
+use dom::element::{HTMLHtmlElementTypeId, HTMLHeadElementTypeId, HTMLTitleElementTypeId};
+use dom::element::{HTMLBodyElementTypeId, HTMLFrameSetElementTypeId};
+use dom::event::Event;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlcollection::HTMLCollection;
-use dom::htmldocument::HTMLDocument;
+use dom::htmlelement::HTMLElement;
+use dom::htmlheadelement::HTMLHeadElement;
+use dom::htmlhtmlelement::HTMLHtmlElement;
+use dom::htmltitleelement::HTMLTitleElement;
 use dom::mouseevent::MouseEvent;
-use dom::node::{AbstractNode, Node, ElementNodeTypeId, DocumentNodeTypeId};
+use dom::node::{Node, ElementNodeTypeId, DocumentNodeTypeId, NodeHelpers, INode};
 use dom::text::Text;
 use dom::processinginstruction::ProcessingInstruction;
 use dom::uievent::UIEvent;
 use dom::window::Window;
-use dom::htmltitleelement::HTMLTitleElement;
 use html::hubbub_html_parser::build_element_from_tag;
 use hubbub::hubbub::{QuirksMode, NoQuirks, LimitedQuirks, FullQuirks};
 use layout_interface::{DocumentDamageLevel, ContentChangedDocumentDamage};
@@ -28,154 +38,109 @@ use servo_util::namespace::Null;
 use servo_util::str::DOMString;
 
 use extra::url::{Url, from_str};
-use js::jsapi::{JSObject, JSContext, JSTracer};
+use js::jsapi::{JSObject, JSContext};
 use std::ascii::StrAsciiExt;
-use std::cast;
 use std::hashmap::HashMap;
-use std::unstable::raw::Box;
-
-#[deriving(Eq)]
-pub enum DocumentTypeId {
-    PlainDocumentTypeId,
-    HTMLDocumentTypeId
-}
-
-#[deriving(Eq)]
-pub struct AbstractDocument {
-    document: *mut Box<Document>
-}
-
-impl AbstractDocument {
-    pub fn document<'a>(&'a self) -> &'a Document {
-        unsafe {
-            &(*self.document).data
-        }
-    }
-
-    pub fn mut_document<'a>(&'a self) -> &'a mut Document {
-        unsafe {
-            &mut (*self.document).data
-        }
-    }
-
-    unsafe fn transmute<T, R>(&self, f: |&T| -> R) -> R {
-        let box_: *Box<T> = cast::transmute(self.document);
-        f(&(*box_).data)
-    }
 
-    pub fn with_html<R>(&self, callback: |&HTMLDocument| -> R) -> R {
-        match self.document().doctype {
-            HTML => unsafe { self.transmute(callback) },
-            _ => fail!("attempt to downcast a non-HTMLDocument to HTMLDocument")
-        }
-    }
-
-    pub fn from_box<T>(ptr: *mut Box<T>) -> AbstractDocument {
-        AbstractDocument {
-            document: ptr as *mut Box<Document>
-        }
-    }
-
-    pub fn from_node(node: AbstractNode) -> AbstractDocument {
-        if !node.is_document() {
-            fail!("node is not a document");
-        }
-        unsafe {
-            cast::transmute(node)
-        }
-    }
-}
+use extra::serialize::{Encoder, Encodable};
 
-#[deriving(Eq)]
-pub enum DocumentType {
-    HTML,
-    SVG,
-    XML
+#[deriving(Eq,Encodable)]
+pub enum IsHTMLDocument {
+    HTMLDocument,
+    NonHTMLDocument,
 }
 
+#[deriving(Encodable)]
 pub struct Document {
     node: Node,
     reflector_: Reflector,
-    window: @mut Window,
-    doctype: DocumentType,
-    idmap: HashMap<DOMString, AbstractNode>,
-    implementation: Option<@mut DOMImplementation>,
+    window: JS<Window>,
+    idmap: HashMap<DOMString, JS<Element>>,
+    implementation: Option<JS<DOMImplementation>>,
     content_type: DOMString,
+    encoding_name: DOMString,
+    is_html_document: bool,
+    extra: Untraceable,
+}
+
+struct Untraceable {
     url: Url,
     quirks_mode: QuirksMode,
-    encoding_name: DOMString,
+}
+
+impl<S: Encoder> Encodable<S> for Untraceable {
+    fn encode(&self, _: &mut S) {
+    }
+}
+
+impl DocumentDerived for EventTarget {
+    fn is_document(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(DocumentNodeTypeId) => true,
+            _ => false
+        }
+    }
 }
 
 impl Document {
-    pub fn reflect_document<D: Reflectable>
-            (document:  @mut D,
-             window:    @mut Window,
-             wrap_fn:   extern "Rust" fn(*JSContext, *JSObject, @mut D) -> *JSObject)
-             -> AbstractDocument {
+    pub fn reflect_document<D: Reflectable+DocumentBase>
+            (document:  ~D,
+             window:    &JS<Window>,
+             wrap_fn:   extern "Rust" fn(*JSContext, *JSObject, ~D) -> *JSObject)
+             -> JS<D> {
         assert!(document.reflector().get_jsobject().is_null());
-        let document = reflect_dom_object(document, window, wrap_fn);
-        assert!(document.reflector().get_jsobject().is_not_null());
-
-        // JS object now owns the Document, so transmute_copy is needed
-        let abstract = AbstractDocument {
-            document: unsafe { cast::transmute_copy(&document) }
-        };
-        abstract.mut_document().node.set_owner_doc(abstract);
-        abstract
-    }
-
-    pub fn new_inherited(window: @mut Window, url: Option<Url>, doctype: DocumentType, content_type: Option<DOMString>) -> Document {
-        let node_type = match doctype {
-            HTML => HTMLDocumentTypeId,
-            SVG | XML => PlainDocumentTypeId
-        };
+        let raw_doc = reflect_dom_object(document, window.get(), wrap_fn);
+        assert!(raw_doc.reflector().get_jsobject().is_not_null());
+
+        let document = DocumentCast::from(&raw_doc);
+        let mut node: JS<Node> = NodeCast::from(&document);
+        node.get_mut().set_owner_doc(&document);
+        raw_doc
+    }
+
+    pub fn new_inherited(window: JS<Window>,
+                         url: Option<Url>,
+                         is_html_document: IsHTMLDocument,
+                         content_type: Option<DOMString>) -> Document {
         Document {
-            node: Node::new_without_doc(DocumentNodeTypeId(node_type)),
+            node: Node::new_without_doc(DocumentNodeTypeId),
             reflector_: Reflector::new(),
             window: window,
-            doctype: doctype,
             idmap: HashMap::new(),
             implementation: None,
             content_type: match content_type {
                 Some(string) => string.clone(),
-                None => match doctype {
+                None => match is_html_document {
                     // http://dom.spec.whatwg.org/#dom-domimplementation-createhtmldocument
-                    HTML => ~"text/html",
+                    HTMLDocument => ~"text/html",
                     // http://dom.spec.whatwg.org/#concept-document-content-type
-                    SVG | XML => ~"application/xml"
+                    NonHTMLDocument => ~"application/xml"
                 }
             },
-            url: match url {
-                None => from_str("about:blank").unwrap(),
-                Some(_url) => _url
+            extra: Untraceable {
+                url: match url {
+                    None => from_str("about:blank").unwrap(),
+                    Some(_url) => _url
+                },
+                // http://dom.spec.whatwg.org/#concept-document-quirks
+                quirks_mode: NoQuirks,
             },
-            // http://dom.spec.whatwg.org/#concept-document-quirks
-            quirks_mode: NoQuirks,
             // http://dom.spec.whatwg.org/#concept-document-encoding
             encoding_name: ~"utf-8",
+            is_html_document: is_html_document == HTMLDocument,
         }
     }
 
-    pub fn new(window: @mut Window, url: Option<Url>, doctype: DocumentType, content_type: Option<DOMString>) -> AbstractDocument {
-        let document = Document::new_inherited(window, url, doctype, content_type);
-        Document::reflect_document(@mut document, window, DocumentBinding::Wrap)
+    pub fn new(window: &JS<Window>, url: Option<Url>, doctype: IsHTMLDocument, content_type: Option<DOMString>) -> JS<Document> {
+        let document = Document::new_inherited(window.clone(), url, doctype, content_type);
+        Document::reflect_document(~document, window, DocumentBinding::Wrap)
     }
 }
 
 impl Document {
     // http://dom.spec.whatwg.org/#dom-document
-    pub fn Constructor(owner: @mut Window) -> Fallible<AbstractDocument> {
-        Ok(Document::new(owner, None, XML, None))
-    }
-}
-
-impl Reflectable for AbstractDocument {
-    fn reflector<'a>(&'a self) -> &'a Reflector {
-        self.document().reflector()
-    }
-
-    fn mut_reflector<'a>(&'a mut self) -> &'a mut Reflector {
-        self.mut_document().mut_reflector()
+    pub fn Constructor(owner: &JS<Window>) -> Fallible<JS<Document>> {
+        Ok(Document::new(owner, None, NonHTMLDocument, None))
     }
 }
 
@@ -191,16 +156,16 @@ impl Reflectable for Document {
 
 impl Document {
     // http://dom.spec.whatwg.org/#dom-document-implementation
-    pub fn Implementation(&mut self) -> @mut DOMImplementation {
+    pub fn Implementation(&mut self) -> JS<DOMImplementation> {
         if self.implementation.is_none() {
-            self.implementation = Some(DOMImplementation::new(self.window));
+            self.implementation = Some(DOMImplementation::new(&self.window));
         }
-        self.implementation.unwrap()
+        self.implementation.get_ref().clone()
     }
 
     // http://dom.spec.whatwg.org/#dom-document-url
     pub fn URL(&self) -> DOMString {
-        self.url.to_str()
+        self.extra.url.to_str()
     }
 
     // http://dom.spec.whatwg.org/#dom-document-documenturi
@@ -210,14 +175,14 @@ impl Document {
 
     // http://dom.spec.whatwg.org/#dom-document-compatmode
     pub fn CompatMode(&self) -> DOMString {
-        match self.quirks_mode {
+        match self.extra.quirks_mode {
             NoQuirks => ~"CSS1Compat",
             LimitedQuirks | FullQuirks => ~"BackCompat"
         }
     }
 
     pub fn set_quirks_mode(&mut self, mode: QuirksMode) {
-        self.quirks_mode = mode;
+        self.extra.quirks_mode = mode;
     }
 
     // http://dom.spec.whatwg.org/#dom-document-characterset
@@ -235,43 +200,34 @@ impl Document {
     }
 
     // http://dom.spec.whatwg.org/#dom-document-doctype
-    pub fn GetDoctype(&self) -> Option<AbstractNode> {
+    pub fn GetDoctype(&self) -> Option<JS<DocumentType>> {
         self.node.children().find(|child| child.is_doctype())
+                            .map(|node| DocumentTypeCast::to(&node))
     }
 
     // http://dom.spec.whatwg.org/#dom-document-documentelement
-    pub fn GetDocumentElement(&self) -> Option<AbstractNode> {
+    pub fn GetDocumentElement(&self) -> Option<JS<Element>> {
         self.node.child_elements().next()
     }
 
     // http://dom.spec.whatwg.org/#dom-document-getelementsbytagname
-    pub fn GetElementsByTagName(&self, tag: DOMString) -> @mut HTMLCollection {
+    pub fn GetElementsByTagName(&self, tag: DOMString) -> JS<HTMLCollection> {
         self.createHTMLCollection(|elem| elem.tag_name == tag)
     }
 
-    // http://dom.spec.whatwg.org/#dom-document-getelementsbytagnamens
-    pub fn GetElementsByTagNameNS(&self, _ns: Option<DOMString>, _tag: DOMString) -> @mut HTMLCollection {
-        HTMLCollection::new(self.window, ~[])
-    }
-
-    // http://dom.spec.whatwg.org/#dom-document-getelementsbyclassname
-    pub fn GetElementsByClassName(&self, _class: DOMString) -> @mut HTMLCollection {
-        HTMLCollection::new(self.window, ~[])
-    }
-
     // http://dom.spec.whatwg.org/#dom-nonelementparentnode-getelementbyid
-    pub fn GetElementById(&self, id: DOMString) -> Option<AbstractNode> {
+    pub fn GetElementById(&self, id: DOMString) -> Option<JS<Element>> {
         // TODO: "in tree order, within the context object's tree"
         // http://dom.spec.whatwg.org/#dom-document-getelementbyid.
         match self.idmap.find_equiv(&id) {
             None => None,
-            Some(node) => Some(*node),
+            Some(node) => Some(node.clone()),
         }
     }
 
     // http://dom.spec.whatwg.org/#dom-document-createelement
-    pub fn CreateElement(&self, abstract_self: AbstractDocument, local_name: DOMString)
-                         -> Fallible<AbstractNode> {
+    pub fn CreateElement(&self, abstract_self: &JS<Document>, local_name: DOMString)
+                         -> Fallible<JS<Element>> {
         if xml_name_type(local_name) == InvalidXMLName {
             debug!("Not a valid element name");
             return Err(InvalidCharacter);
@@ -281,24 +237,24 @@ impl Document {
     }
 
     // http://dom.spec.whatwg.org/#dom-document-createdocumentfragment
-    pub fn CreateDocumentFragment(&self, abstract_self: AbstractDocument) -> AbstractNode {
+    pub fn CreateDocumentFragment(&self, abstract_self: &JS<Document>) -> JS<DocumentFragment> {
         DocumentFragment::new(abstract_self)
     }
 
     // http://dom.spec.whatwg.org/#dom-document-createtextnode
-    pub fn CreateTextNode(&self, abstract_self: AbstractDocument, data: DOMString)
-                          -> AbstractNode {
+    pub fn CreateTextNode(&self, abstract_self: &JS<Document>, data: DOMString)
+                          -> JS<Text> {
         Text::new(data, abstract_self)
     }
 
     // http://dom.spec.whatwg.org/#dom-document-createcomment
-    pub fn CreateComment(&self, abstract_self: AbstractDocument, data: DOMString) -> AbstractNode {
+    pub fn CreateComment(&self, abstract_self: &JS<Document>, data: DOMString) -> JS<Comment> {
         Comment::new(data, abstract_self)
     }
 
     // http://dom.spec.whatwg.org/#dom-document-createprocessinginstruction
-    pub fn CreateProcessingInstruction(&self, abstract_self: AbstractDocument, target: DOMString,
-                                       data: DOMString) -> Fallible<AbstractNode> {
+    pub fn CreateProcessingInstruction(&self, abstract_self: &JS<Document>, target: DOMString,
+                                       data: DOMString) -> Fallible<JS<ProcessingInstruction>> {
         // Step 1.
         if xml_name_type(target) == InvalidXMLName {
             return Err(InvalidCharacter);
@@ -314,43 +270,29 @@ impl Document {
     }
 
     // http://dom.spec.whatwg.org/#dom-document-createevent
-    pub fn CreateEvent(&self, interface: DOMString) -> Fallible<AbstractEvent> {
+    pub fn CreateEvent(&self, interface: DOMString) -> Fallible<JS<Event>> {
         match interface.as_slice() {
-            "UIEvents" => Ok(UIEvent::new(self.window)),
-            "MouseEvents" => Ok(MouseEvent::new(self.window)),
-            "HTMLEvents" => Ok(Event::new(self.window)),
+            "UIEvents" => Ok(EventCast::from(&UIEvent::new(&self.window))),
+            "MouseEvents" => Ok(EventCast::from(&MouseEvent::new(&self.window))),
+            "HTMLEvents" => Ok(Event::new(&self.window)),
             _ => Err(NotSupported)
         }
     }
 
     // http://www.whatwg.org/specs/web-apps/current-work/#document.title
-    pub fn Title(&self, _: AbstractDocument) -> DOMString {
+    pub fn Title(&self, _: &JS<Document>) -> DOMString {
         let mut title = ~"";
-        match self.doctype {
-            SVG => {
-                fail!("no SVG document yet")
-            },
-            _ => {
-                match self.GetDocumentElement() {
-                    None => {},
-                    Some(root) => {
-                        for node in root.traverse_preorder() {
-                            if node.type_id() != ElementNodeTypeId(HTMLTitleElementTypeId) {
-                                continue;
-                            }
-                            for child in node.children() {
-                                if child.is_text() {
-                                    child.with_imm_text(|text| {
-                                        title.push_str(text.characterdata.data.as_slice());
-                                    });
-                                }
-                            }
-                            break;
-                        }
+        self.GetDocumentElement().map(|root| {
+            let root: JS<Node> = NodeCast::from(&root);
+            root.traverse_preorder()
+                .find(|node| node.type_id() == ElementNodeTypeId(HTMLTitleElementTypeId))
+                .map(|title_elem| {
+                    for child in title_elem.children() {
+                        let text: JS<Text> = TextCast::to(&child);
+                        title.push_str(text.get().characterdata.data.as_slice());
                     }
-                }
-            }
-        }
+                });
+        });
         let v: ~[&str] = title.words().collect();
         title = v.connect(" ");
         title = title.trim().to_owned();
@@ -358,85 +300,74 @@ impl Document {
     }
 
     // http://www.whatwg.org/specs/web-apps/current-work/#document.title
-    pub fn SetTitle(&self, abstract_self: AbstractDocument, title: DOMString) -> ErrorResult {
-        match self.doctype {
-            SVG => {
-                fail!("no SVG document yet")
-            },
-            _ => {
-                match self.GetDocumentElement() {
-                    None => {},
-                    Some(root) => {
-                        for node in root.traverse_preorder() {
-                            if node.type_id() != ElementNodeTypeId(HTMLHeadElementTypeId) {
-                                continue;
-                            }
-                            let mut has_title = false;
-                            for child in node.children() {
-                                if child.type_id() != ElementNodeTypeId(HTMLTitleElementTypeId) {
-                                    continue;
-                                }
-                                has_title = true;
-                                for title_child in child.children() {
-                                    child.RemoveChild(title_child);
-                                }
-                                child.AppendChild(self.CreateTextNode(abstract_self, title.clone()));
-                                break;
-                            }
-                            if !has_title {
-                                let new_title = HTMLTitleElement::new(~"title", abstract_self);
-                                new_title.AppendChild(self.CreateTextNode(abstract_self, title.clone()));
-                                node.AppendChild(new_title);
-                            }
-                            break;
-                        }
+    pub fn SetTitle(&self, abstract_self: &JS<Document>, title: DOMString) -> ErrorResult {
+        self.GetDocumentElement().map(|root| {
+            let root: JS<Node> = NodeCast::from(&root);
+            let mut head_node = root.traverse_preorder().find(|child| {
+                child.get().type_id == ElementNodeTypeId(HTMLHeadElementTypeId)
+            });
+            head_node.as_mut().map(|head| {
+
+                let mut title_node = head.children().find(|child| {
+                    child.get().type_id == ElementNodeTypeId(HTMLTitleElementTypeId)
+                });
+
+                title_node.as_mut().map(|title_node| {
+                    for mut title_child in title_node.children() {
+                        title_node.RemoveChild(&mut title_child);
                     }
+                    let new_text = self.CreateTextNode(abstract_self, title.clone());
+                    title_node.AppendChild(&mut NodeCast::from(&new_text));
+                });
+
+                if title_node.is_none() {
+                    let mut new_title: JS<Node> =
+                        NodeCast::from(&HTMLTitleElement::new(~"title", abstract_self));
+                    let new_text = self.CreateTextNode(abstract_self, title.clone());
+                    new_title.AppendChild(&mut NodeCast::from(&new_text));
+                    head.AppendChild(&mut new_title);
                 }
-            }
-        }
+            });
+        });
         Ok(())
     }
 
-    fn get_html_element(&self) -> Option<AbstractNode> {
+    fn get_html_element(&self) -> Option<JS<HTMLHtmlElement>> {
         self.GetDocumentElement().filtered(|root| {
-            match root.type_id() {
-                ElementNodeTypeId(HTMLHtmlElementTypeId) => true,
-                _ => false
-            }
-        })
+            root.get().node.type_id == ElementNodeTypeId(HTMLHtmlElementTypeId)
+        }).map(|elem| HTMLHtmlElementCast::to(&elem))
     }
 
     // http://www.whatwg.org/specs/web-apps/current-work/#dom-document-head
-    pub fn GetHead(&self) -> Option<AbstractNode> {
+    pub fn GetHead(&self) -> Option<JS<HTMLHeadElement>> {
         self.get_html_element().and_then(|root| {
-            root.children().find(|child| {
+            let node: JS<Node> = NodeCast::from(&root);
+            node.children().find(|child| {
                 child.type_id() == ElementNodeTypeId(HTMLHeadElementTypeId)
-            })
+            }).map(|node| HTMLHeadElementCast::to(&node))
         })
     }
 
     // http://www.whatwg.org/specs/web-apps/current-work/#dom-document-body
-    pub fn GetBody(&self, _: AbstractDocument) -> Option<AbstractNode> {
-        match self.get_html_element() {
-            None => None,
-            Some(root) => {
-                root.children().find(|child| {
-                    match child.type_id() {
-                        ElementNodeTypeId(HTMLBodyElementTypeId) |
-                        ElementNodeTypeId(HTMLFrameSetElementTypeId) => true,
-                        _ => false
-                    }
-                })
-            }
-        }
+    pub fn GetBody(&self, _: &JS<Document>) -> Option<JS<HTMLElement>> {
+        self.get_html_element().and_then(|root| {
+            let node: JS<Node> = NodeCast::from(&root);
+            node.children().find(|child| {
+                match child.type_id() {
+                    ElementNodeTypeId(HTMLBodyElementTypeId) |
+                    ElementNodeTypeId(HTMLFrameSetElementTypeId) => true,
+                    _ => false
+                }
+            }).map(|node| HTMLElementCast::to(&node))
+        })
     }
 
     // http://www.whatwg.org/specs/web-apps/current-work/#dom-document-body
-    pub fn SetBody(&self, abstract_self: AbstractDocument, new_body: Option<AbstractNode>) -> ErrorResult {
+    pub fn SetBody(&self, abstract_self: &JS<Document>, new_body: Option<JS<HTMLElement>>) -> ErrorResult {
         // Step 1.
         match new_body {
-            Some(node) => {
-                match node.type_id() {
+            Some(ref node) => {
+                match node.get().element.node.type_id {
                     ElementNodeTypeId(HTMLBodyElementTypeId) | ElementNodeTypeId(HTMLFrameSetElementTypeId) => {}
                     _ => return Err(HierarchyRequest)
                 }
@@ -445,7 +376,7 @@ impl Document {
         }
 
         // Step 2.
-        let old_body: Option<AbstractNode> = self.GetBody(abstract_self);
+        let old_body: Option<JS<HTMLElement>> = self.GetBody(abstract_self);
         if old_body == new_body {
             return Ok(());
         }
@@ -455,41 +386,84 @@ impl Document {
             // Step 4.
             None => return Err(HierarchyRequest),
             Some(root) => {
+                let mut new_body: JS<Node> = NodeCast::from(&new_body.unwrap());
+                let mut root: JS<Node> = NodeCast::from(&root);
                 match old_body {
-                    Some(child) => { root.ReplaceChild(new_body.unwrap(), child); }
-                    None => { root.AppendChild(new_body.unwrap()); }
-                }
+                    Some(child) => {
+                        let mut child: JS<Node> = NodeCast::from(&child);
+                        root.ReplaceChild(&mut new_body, &mut child)
+                    }
+                    None => root.AppendChild(&mut new_body)
+                };
             }
         }
         Ok(())
     }
 
     // http://www.whatwg.org/specs/web-apps/current-work/#dom-document-getelementsbyname
-    pub fn GetElementsByName(&self, name: DOMString) -> @mut HTMLCollection {
+    pub fn GetElementsByName(&self, name: DOMString) -> JS<HTMLCollection> {
         self.createHTMLCollection(|elem| {
             elem.get_attribute(Null, "name").map_default(false, |attr| {
-                attr.value_ref() == name
+                attr.get().value_ref() == name
             })
         })
     }
 
-    pub fn createHTMLCollection(&self, callback: |elem: &Element| -> bool) -> @mut HTMLCollection {
+    pub fn Images(&self) -> JS<HTMLCollection> {
+        self.createHTMLCollection(|elem| "img" == elem.tag_name)
+    }
+
+    pub fn Embeds(&self) -> JS<HTMLCollection> {
+        self.createHTMLCollection(|elem| "embed" == elem.tag_name)
+    }
+
+    pub fn Plugins(&self) -> JS<HTMLCollection> {
+        self.Embeds()
+    }
+
+    pub fn Links(&self) -> JS<HTMLCollection> {
+        self.createHTMLCollection(|elem| {
+            ("a" == elem.tag_name || "area" == elem.tag_name) &&
+            elem.get_attribute(Null, "href").is_some()
+        })
+    }
+
+    pub fn Forms(&self) -> JS<HTMLCollection> {
+        self.createHTMLCollection(|elem| "form" == elem.tag_name)
+    }
+
+    pub fn Scripts(&self) -> JS<HTMLCollection> {
+        self.createHTMLCollection(|elem| "script" == elem.tag_name)
+    }
+
+    pub fn Anchors(&self) -> JS<HTMLCollection> {
+        self.createHTMLCollection(|elem| {
+            "a" == elem.tag_name && elem.get_attribute(Null, "name").is_some()
+        })
+    }
+
+    pub fn Applets(&self) -> JS<HTMLCollection> {
+        // FIXME: This should be return OBJECT elements containing applets.
+        self.createHTMLCollection(|elem| "applet" == elem.tag_name)
+    }
+
+    pub fn createHTMLCollection(&self, callback: |elem: &Element| -> bool) -> JS<HTMLCollection> {
         let mut elements = ~[];
         match self.GetDocumentElement() {
             None => {},
             Some(root) => {
+                let root: JS<Node> = NodeCast::from(&root);
                 for child in root.traverse_preorder() {
                     if child.is_element() {
-                        child.with_imm_element(|elem| {
-                            if callback(elem) {
-                                elements.push(child);
-                            }
-                        });
+                        let elem: JS<Element> = ElementCast::to(&child);
+                        if callback(elem.get()) {
+                            elements.push(elem);
+                        }
                     }
                 }
             }
         }
-        HTMLCollection::new(self.window, elements)
+        HTMLCollection::new(&self.window, elements)
     }
 
     pub fn content_changed(&self) {
@@ -497,22 +471,22 @@ impl Document {
     }
 
     pub fn damage_and_reflow(&self, damage: DocumentDamageLevel) {
-        self.window.damage_and_reflow(damage);
+        self.window.get().damage_and_reflow(damage);
     }
 
     pub fn wait_until_safe_to_modify_dom(&self) {
-        self.window.wait_until_safe_to_modify_dom();
+        self.window.get().wait_until_safe_to_modify_dom();
     }
 
-    pub fn register_nodes_with_id(&mut self, root: &AbstractNode) {
-        foreach_ided_elements(root, |id: &DOMString, abstract_node: &AbstractNode| {
+    pub fn register_nodes_with_id(&mut self, root: &JS<Element>) {
+        foreach_ided_elements(root, |id: &DOMString, abstract_node: &JS<Element>| {
             // TODO: "in tree order, within the context object's tree"
             // http://dom.spec.whatwg.org/#dom-document-getelementbyid.
-            self.idmap.find_or_insert(id.clone(), *abstract_node);
+            self.idmap.find_or_insert(id.clone(), abstract_node.clone());
         });
     }
 
-    pub fn unregister_nodes_with_id(&mut self, root: &AbstractNode) {
+    pub fn unregister_nodes_with_id(&mut self, root: &JS<Element>) {
         foreach_ided_elements(root, |id: &DOMString, _| {
             // TODO: "in tree order, within the context object's tree"
             // http://dom.spec.whatwg.org/#dom-document-getelementbyid.
@@ -521,7 +495,7 @@ impl Document {
     }
 
     pub fn update_idmap(&mut self,
-                        abstract_self: AbstractNode,
+                        abstract_self: &JS<Element>,
                         new_id: Option<DOMString>,
                         old_id: Option<DOMString>) {
         // remove old ids:
@@ -539,11 +513,11 @@ impl Document {
             Some(new_id) => {
                 // TODO: support the case if multiple elements
                 // which haves same id are in the same document.
-                self.idmap.mangle(new_id, abstract_self,
-                                  |_, new_node: AbstractNode| -> AbstractNode {
+                self.idmap.mangle(new_id, abstract_self.clone(),
+                                  |_, new_node: JS<Element>| -> JS<Element> {
                                       new_node
                                   },
-                                  |_, old_node: &mut AbstractNode, new_node: AbstractNode| {
+                                  |_, old_node: &mut JS<Element>, new_node: JS<Element>| {
                                       *old_node = new_node;
                                   });
             }
@@ -553,25 +527,19 @@ impl Document {
 }
 
 #[inline(always)]
-fn foreach_ided_elements(root: &AbstractNode, callback: |&DOMString, &AbstractNode|) {
+fn foreach_ided_elements(root: &JS<Element>, callback: |&DOMString, &JS<Element>|) {
+    let root: JS<Node> = NodeCast::from(root);
     for node in root.traverse_preorder() {
         if !node.is_element() {
             continue;
         }
 
-        node.with_imm_element(|element| {
-            match element.get_attribute(Null, "id") {
-                Some(id) => {
-                    callback(&id.Value(), &node);
-                }
-                None => ()
+        let element: JS<Element> = ElementCast::to(&node);
+        match element.get().get_attribute(Null, "id") {
+            Some(id) => {
+                callback(&id.get().Value(), &element);
             }
-        });
-    }
-}
-
-impl Traceable for Document {
-    fn trace(&self, tracer: *mut JSTracer) {
-        self.node.trace(tracer);
+            None => ()
+        }
     }
 }
diff --git a/src/components/script/dom/documentfragment.rs b/src/components/script/dom/documentfragment.rs
index 0b4c56d2c92..0e38b72f8ea 100644
--- a/src/components/script/dom/documentfragment.rs
+++ b/src/components/script/dom/documentfragment.rs
@@ -2,32 +2,45 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::codegen::InheritTypes::DocumentFragmentDerived;
 use dom::bindings::codegen::DocumentFragmentBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::Fallible;
-use dom::document::AbstractDocument;
-use dom::node::{AbstractNode, DocumentFragmentNodeTypeId, Node};
+use dom::document::Document;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::node::{DocumentFragmentNodeTypeId, Node};
 use dom::window::Window;
 
+#[deriving(Encodable)]
 pub struct DocumentFragment {
     node: Node,
 }
 
+impl DocumentFragmentDerived for EventTarget {
+    fn is_documentfragment(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(DocumentFragmentNodeTypeId) => true,
+            _ => false
+        }
+    }
+}
+
 impl DocumentFragment {
     /// Creates a new DocumentFragment.
-    pub fn new_inherited(document: AbstractDocument) -> DocumentFragment {
+    pub fn new_inherited(document: JS<Document>) -> DocumentFragment {
         DocumentFragment {
             node: Node::new_inherited(DocumentFragmentNodeTypeId, document),
         }
     }
 
-    pub fn new(document: AbstractDocument) -> AbstractNode {
-        let node = DocumentFragment::new_inherited(document);
-        Node::reflect_node(@mut node, document, DocumentFragmentBinding::Wrap)
+    pub fn new(document: &JS<Document>) -> JS<DocumentFragment> {
+        let node = DocumentFragment::new_inherited(document.clone());
+        Node::reflect_node(~node, document, DocumentFragmentBinding::Wrap)
     }
 }
 
 impl DocumentFragment {
-    pub fn Constructor(owner: @mut Window) -> Fallible<AbstractNode> {
-        Ok(DocumentFragment::new(owner.Document()))
+    pub fn Constructor(owner: &JS<Window>) -> Fallible<JS<DocumentFragment>> {
+        Ok(DocumentFragment::new(&owner.get().Document()))
     }
 }
diff --git a/src/components/script/dom/documenttype.rs b/src/components/script/dom/documenttype.rs
index f161b287702..3892f2a3235 100644
--- a/src/components/script/dom/documenttype.rs
+++ b/src/components/script/dom/documenttype.rs
@@ -2,12 +2,16 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::codegen::InheritTypes::DocumentTypeDerived;
 use dom::bindings::codegen::DocumentTypeBinding;
-use dom::document::AbstractDocument;
-use dom::node::{AbstractNode, Node, DoctypeNodeTypeId};
+use dom::bindings::js::JS;
+use dom::document::Document;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::node::{Node, DoctypeNodeTypeId};
 use servo_util::str::DOMString;
 
 /// The `DOCTYPE` tag.
+#[deriving(Encodable)]
 pub struct DocumentType {
     node: Node,
     name: DOMString,
@@ -15,11 +19,20 @@ pub struct DocumentType {
     system_id: DOMString,
 }
 
+impl DocumentTypeDerived for EventTarget {
+    fn is_documenttype(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(DoctypeNodeTypeId) => true,
+            _ => false
+        }
+    }
+}
+
 impl DocumentType {
     pub fn new_inherited(name: DOMString,
                          public_id: Option<DOMString>,
                          system_id: Option<DOMString>,
-                         document: AbstractDocument)
+                         document: JS<Document>)
             -> DocumentType {
         DocumentType {
             node: Node::new_inherited(DoctypeNodeTypeId, document),
@@ -32,13 +45,13 @@ impl DocumentType {
     pub fn new(name: DOMString,
                public_id: Option<DOMString>,
                system_id: Option<DOMString>,
-               document: AbstractDocument)
-               -> AbstractNode {
+               document: &JS<Document>)
+               -> JS<DocumentType> {
         let documenttype = DocumentType::new_inherited(name,
                                                        public_id,
                                                        system_id,
-                                                       document);
-        Node::reflect_node(@mut documenttype, document, DocumentTypeBinding::Wrap)
+                                                       document.clone());
+        Node::reflect_node(~documenttype, document, DocumentTypeBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/domexception.rs b/src/components/script/dom/domexception.rs
index f0801fee40f..f6eb1751adc 100644
--- a/src/components/script/dom/domexception.rs
+++ b/src/components/script/dom/domexception.rs
@@ -3,12 +3,13 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::DOMExceptionBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::window::Window;
 use servo_util::str::DOMString;
 
 #[repr(uint)]
-#[deriving(ToStr)]
+#[deriving(ToStr, Encodable)]
 enum DOMErrorName {
     IndexSizeError = 1,
     HierarchyRequestError = 3,
@@ -33,6 +34,7 @@ enum DOMErrorName {
     EncodingError
 }
 
+#[deriving(Encodable)]
 pub struct DOMException {
     code: DOMErrorName,
     reflector_: Reflector
@@ -46,8 +48,8 @@ impl DOMException {
         }
     }
 
-    pub fn new(window: &Window, code: DOMErrorName) -> @mut DOMException {
-        reflect_dom_object(@mut DOMException::new_inherited(code), window, DOMExceptionBinding::Wrap)
+    pub fn new(window: &Window, code: DOMErrorName) -> JS<DOMException> {
+        reflect_dom_object(~DOMException::new_inherited(code), window, DOMExceptionBinding::Wrap)
     }
 }
 
@@ -67,7 +69,7 @@ impl DOMException {
         match self.code {
             // http://dom.spec.whatwg.org/#concept-throw
             EncodingError => 0,
-            _ => self.code as u16
+            code => code as u16
         }
     }
 
diff --git a/src/components/script/dom/domimplementation.rs b/src/components/script/dom/domimplementation.rs
index 8595d54c065..86968680741 100644
--- a/src/components/script/dom/domimplementation.rs
+++ b/src/components/script/dom/domimplementation.rs
@@ -3,36 +3,38 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::DOMImplementationBinding;
+use dom::bindings::codegen::InheritTypes::NodeCast;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflector, Reflectable, reflect_dom_object};
 use dom::bindings::utils::{Fallible, InvalidCharacter, NamespaceError};
 use dom::bindings::utils::{QName, Name, InvalidXMLName, xml_name_type};
-use dom::document::{AbstractDocument, HTML, HTMLDocumentTypeId};
+use dom::document::{Document, HTMLDocument};
 use dom::documenttype::DocumentType;
-use dom::htmldocument::HTMLDocument;
 use dom::htmlbodyelement::HTMLBodyElement;
 use dom::htmlheadelement::HTMLHeadElement;
 use dom::htmlhtmlelement::HTMLHtmlElement;
 use dom::htmltitleelement::HTMLTitleElement;
-use dom::node::{AbstractNode, DocumentNodeTypeId};
+use dom::node::{Node, INode};
 use dom::text::Text;
 use dom::window::Window;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct DOMImplementation {
-    owner: @mut Window,
-    reflector_: Reflector
+    owner: JS<Window>,
+    reflector_: Reflector,
 }
 
 impl DOMImplementation {
-    pub fn new_inherited(owner: @mut Window) -> DOMImplementation {
+    pub fn new_inherited(owner: JS<Window>) -> DOMImplementation {
         DOMImplementation {
             owner: owner,
-            reflector_: Reflector::new()
+            reflector_: Reflector::new(),
         }
     }
 
-    pub fn new(owner: @mut Window) -> @mut DOMImplementation {
-        reflect_dom_object(@mut DOMImplementation::new_inherited(owner), owner,
+    pub fn new(owner: &JS<Window>) -> JS<DOMImplementation> {
+        reflect_dom_object(~DOMImplementation::new_inherited(owner.clone()), owner.get(),
                            DOMImplementationBinding::Wrap)
     }
 }
@@ -50,66 +52,63 @@ impl Reflectable for DOMImplementation {
 // http://dom.spec.whatwg.org/#domimplementation
 impl DOMImplementation {
     // http://dom.spec.whatwg.org/#dom-domimplementation-createdocumenttype
-    pub fn CreateDocumentType(&self, qname: DOMString, pubid: DOMString, sysid: DOMString) -> Fallible<AbstractNode> {
+    pub fn CreateDocumentType(&self, qname: DOMString, pubid: DOMString, sysid: DOMString) -> Fallible<JS<DocumentType>> {
         match xml_name_type(qname) {
             // Step 1.
             InvalidXMLName => Err(InvalidCharacter),
             // Step 2.
             Name => Err(NamespaceError),
             // Step 3.
-            QName => Ok(DocumentType::new(qname, Some(pubid), Some(sysid), self.owner.Document()))
+            QName => Ok(DocumentType::new(qname, Some(pubid), Some(sysid), &self.owner.get().Document()))
         }
     }
 
     // http://dom.spec.whatwg.org/#dom-domimplementation-createhtmldocument
-    pub fn CreateHTMLDocument(&self, title: Option<DOMString>) -> AbstractDocument {
+    pub fn CreateHTMLDocument(&self, title: Option<DOMString>) -> JS<Document> {
         // Step 1-2.
-        let abstract_doc = HTMLDocument::new(self.owner, None);
-        assert!(abstract_doc.document().doctype == HTML);
-
-        let abstract_node = AbstractNode::from_document(abstract_doc);
-        assert!(abstract_node.type_id() == DocumentNodeTypeId(HTMLDocumentTypeId));
+        let doc = Document::new(&self.owner, None, HTMLDocument, None);
+        let mut doc_node: JS<Node> = NodeCast::from(&doc);
 
         {
             // Step 3.
-            let doc_type = DocumentType::new(~"html", None, None, abstract_doc);
-            abstract_node.AppendChild(doc_type);
+            let doc_type = DocumentType::new(~"html", None, None, &doc);
+            doc_node.AppendChild(&mut NodeCast::from(&doc_type));
         }
 
         {
             // Step 4.
-            let doc_html = HTMLHtmlElement::new(~"html", abstract_doc);
-            abstract_node.AppendChild(doc_html);
+            let mut doc_html = NodeCast::from(&HTMLHtmlElement::new(~"html", &doc));
+            doc_node.AppendChild(&mut doc_html);
 
             {
                 // Step 5.
-                let doc_head = HTMLHeadElement::new(~"head", abstract_doc);
-                doc_html.AppendChild(doc_head);
+                let mut doc_head = NodeCast::from(&HTMLHeadElement::new(~"head", &doc));
+                doc_html.AppendChild(&mut doc_head);
 
                 // Step 6.
                 match title {
                     None => (),
                     Some(title_str) => {
                         // Step 6.1.
-                        let doc_title = HTMLTitleElement::new(~"title", abstract_doc);
-                        doc_head.AppendChild(doc_title);
+                        let mut doc_title = NodeCast::from(&HTMLTitleElement::new(~"title", &doc));
+                        doc_head.AppendChild(&mut doc_title);
 
                         // Step 6.2.
-                        let title_text = Text::new(title_str, abstract_doc);
-                        doc_title.AppendChild(title_text);
+                        let title_text = Text::new(title_str, &doc);
+                        doc_title.AppendChild(&mut NodeCast::from(&title_text));
                     }
                 }
             }
 
             // Step 7.
-            let doc_body = HTMLBodyElement::new(~"body", abstract_doc);
-            doc_html.AppendChild(doc_body);
+            let doc_body = HTMLBodyElement::new(~"body", &doc);
+            doc_html.AppendChild(&mut NodeCast::from(&doc_body));
         }
 
         // Step 8.
         // FIXME: https://github.com/mozilla/servo/issues/1522
 
         // Step 9.
-        abstract_doc
+        doc
     }
 }
diff --git a/src/components/script/dom/domparser.rs b/src/components/script/dom/domparser.rs
index 1dec0025e8a..f66e737a5f8 100644
--- a/src/components/script/dom/domparser.rs
+++ b/src/components/script/dom/domparser.rs
@@ -4,46 +4,47 @@
 
 use dom::bindings::codegen::DOMParserBinding;
 use dom::bindings::codegen::DOMParserBinding::SupportedTypeValues::{Text_html, Text_xml};
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflector, Reflectable, reflect_dom_object};
 use dom::bindings::utils::Fallible;
 use dom::bindings::utils::FailureUnknown;
-use dom::document::{AbstractDocument, Document};
-use dom::htmldocument::HTMLDocument;
+use dom::document::{Document, HTMLDocument};
 use dom::window::Window;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct DOMParser {
-    owner: @mut Window, //XXXjdm Document instead?
+    owner: JS<Window>, //XXXjdm Document instead?
     reflector_: Reflector
 }
 
 impl DOMParser {
-    pub fn new_inherited(owner: @mut Window) -> DOMParser {
+    pub fn new_inherited(owner: JS<Window>) -> DOMParser {
         DOMParser {
             owner: owner,
             reflector_: Reflector::new()
         }
     }
 
-    pub fn new(owner: @mut Window) -> @mut DOMParser {
-        reflect_dom_object(@mut DOMParser::new_inherited(owner), owner,
+    pub fn new(owner: &JS<Window>) -> JS<DOMParser> {
+        reflect_dom_object(~DOMParser::new_inherited(owner.clone()), owner.get(),
                            DOMParserBinding::Wrap)
     }
 
-    pub fn Constructor(owner: @mut Window) -> Fallible<@mut DOMParser> {
+    pub fn Constructor(owner: &JS<Window>) -> Fallible<JS<DOMParser>> {
         Ok(DOMParser::new(owner))
     }
 
     pub fn ParseFromString(&self,
                            _s: DOMString,
                            ty: DOMParserBinding::SupportedType)
-                           -> Fallible<AbstractDocument> {
+                           -> Fallible<JS<Document>> {
         match ty {
             Text_html => {
-                Ok(HTMLDocument::new(self.owner, None))
+                Ok(Document::new(&self.owner, None, HTMLDocument, None))
             }
             Text_xml => {
-                Document::Constructor(self.owner)
+                Document::Constructor(&self.owner)
             }
             _ => {
                 Err(FailureUnknown)
diff --git a/src/components/script/dom/element.rs b/src/components/script/dom/element.rs
index 12361d7ec85..d7bbaa065a6 100644
--- a/src/components/script/dom/element.rs
+++ b/src/components/script/dom/element.rs
@@ -6,15 +6,22 @@
 
 use dom::attr::Attr;
 use dom::attrlist::AttrList;
+use dom::bindings::codegen::InheritTypes::{ElementDerived, HTMLImageElementCast};
+use dom::bindings::codegen::InheritTypes::{HTMLIFrameElementCast, NodeCast};
+use dom::bindings::codegen::InheritTypes::HTMLObjectElementCast;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector};
 use dom::bindings::utils::{ErrorResult, Fallible, NamespaceError, InvalidCharacter};
 use dom::bindings::utils::{QName, Name, InvalidXMLName, xml_name_type};
 use dom::htmlcollection::HTMLCollection;
 use dom::clientrect::ClientRect;
 use dom::clientrectlist::ClientRectList;
-use dom::document::AbstractDocument;
-use dom::node::{AbstractNode, ElementNodeTypeId, Node, NodeIterator};
-use dom::document;
+use dom::document::Document;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::htmlimageelement::HTMLImageElement;
+use dom::htmliframeelement::HTMLIFrameElement;
+use dom::htmlobjectelement::HTMLObjectElement;
+use dom::node::{ElementNodeTypeId, Node, NodeHelpers, NodeIterator};
 use dom::htmlserializer::serialize;
 use layout_interface::{ContentBoxQuery, ContentBoxResponse, ContentBoxesQuery};
 use layout_interface::{ContentBoxesResponse, ContentChangedDocumentDamage};
@@ -26,15 +33,24 @@ use servo_util::str::{DOMString, null_str_as_empty_ref};
 
 use std::ascii::StrAsciiExt;
 use std::cast;
-use std::unstable::raw::Box;
 
+#[deriving(Encodable)]
 pub struct Element {
     node: Node,
     tag_name: DOMString,     // TODO: This should be an atom, not a DOMString.
     namespace: Namespace,
-    attrs: ~[@mut Attr],
+    attrs: ~[JS<Attr>],
     style_attribute: Option<style::PropertyDeclarationBlock>,
-    attr_list: Option<@mut AttrList>
+    attr_list: Option<JS<AttrList>>
+}
+
+impl ElementDerived for EventTarget {
+    fn is_element(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(_)) => true,
+            _ => false
+        }
+    }
 }
 
 impl Reflectable for Element {
@@ -47,7 +63,7 @@ impl Reflectable for Element {
     }
 }
 
-#[deriving(Eq)]
+#[deriving(Eq,Encodable)]
 pub enum ElementTypeId {
     HTMLElementTypeId,
     HTMLAnchorElementTypeId,
@@ -104,7 +120,6 @@ pub enum ElementTypeId {
     HTMLStyleElementTypeId,
     HTMLTableElementTypeId,
     HTMLTableCaptionElementTypeId,
-    HTMLTableCellElementTypeId,
     HTMLTableDataCellElementTypeId,
     HTMLTableHeaderCellElementTypeId,
     HTMLTableColElementTypeId,
@@ -124,9 +139,8 @@ pub enum ElementTypeId {
 // Element methods
 //
 
-
 impl Element {
-    pub fn new_inherited(type_id: ElementTypeId, tag_name: ~str, namespace: Namespace, document: AbstractDocument) -> Element {
+    pub fn new_inherited(type_id: ElementTypeId, tag_name: ~str, namespace: Namespace, document: JS<Document>) -> Element {
         Element {
             node: Node::new_inherited(ElementNodeTypeId(type_id), document),
             tag_name: tag_name,
@@ -138,41 +152,40 @@ impl Element {
     }
 
     pub fn html_element_in_html_document(&self) -> bool {
-        let owner = self.node.owner_doc();
         self.namespace == namespace::HTML &&
-        // FIXME: check that this matches what the spec calls "is in an HTML document"
-        owner.document().doctype == document::HTML
+        self.node.owner_doc().get().is_html_document
     }
 
     pub fn get_attribute(&self,
                          namespace: Namespace,
-                         name: &str) -> Option<@mut Attr> {
+                         name: &str) -> Option<JS<Attr>> {
         self.attrs.iter().find(|attr| {
+            let attr = attr.get();
             name == attr.local_name && attr.namespace == namespace
-        }).map(|&x| x)
+        }).map(|x| x.clone())
     }
 
     #[inline]
     pub unsafe fn get_attr_val_for_layout(&self, namespace: &Namespace, name: &str)
                                           -> Option<&'static str> {
-        self.attrs.iter().find(|attr: & &@mut Attr| {
+        self.attrs.iter().find(|attr: & &JS<Attr>| {
             // unsafely avoid a borrow because this is accessed by many tasks
             // during parallel layout
-            let attr: ***Box<Attr> = cast::transmute(attr);
-            name == (***attr).data.local_name && (***attr).data.namespace == *namespace
+            let attr: ***Attr = cast::transmute(attr);
+            name == (***attr).local_name && (***attr).namespace == *namespace
        }).map(|attr| {
-            let attr: **Box<Attr> = cast::transmute(attr);
-            cast::transmute((**attr).data.value.as_slice())
+            let attr: **Attr = cast::transmute(attr);
+            cast::transmute((**attr).value.as_slice())
         })
     }
 
-    pub fn set_attr(&mut self, abstract_self: AbstractNode, name: DOMString, value: DOMString)
+    pub fn set_attr(&mut self, abstract_self: &JS<Element>, name: DOMString, value: DOMString)
                     -> ErrorResult {
         self.set_attribute(abstract_self, namespace::Null, name, value)
     }
 
     pub fn set_attribute(&mut self,
-                         abstract_self: AbstractNode,
+                         abstract_self: &JS<Element>,
                          namespace: Namespace,
                          name: DOMString,
                          value: DOMString) -> ErrorResult {
@@ -192,7 +205,8 @@ impl Element {
 
         // FIXME: reduce the time of `value.clone()`.
         let mut old_raw_value: Option<DOMString> = None;
-        for attr in self.attrs.iter() {
+        for attr in self.attrs.mut_iter() {
+            let attr = attr.get_mut();
             if attr.local_name == local_name {
                 old_raw_value = Some(attr.set_value(value.clone()));
                 break;
@@ -200,8 +214,9 @@ impl Element {
         }
 
         if old_raw_value.is_none() {
-            let win = self.node.owner_doc().document().window;
-            let new_attr = Attr::new_ns(win, local_name.clone(), value.clone(),
+            let doc = self.node.owner_doc();
+            let doc = doc.get();
+            let new_attr = Attr::new_ns(doc.window.get(), local_name.clone(), value.clone(),
                                         name.clone(), namespace.clone(),
                                         prefix);
             self.attrs.push(new_attr);
@@ -214,7 +229,7 @@ impl Element {
     }
 
     fn after_set_attr(&mut self,
-                      abstract_self: AbstractNode,
+                      abstract_self: &JS<Element>,
                       local_name: DOMString,
                       value: DOMString,
                       old_value: Option<DOMString>) {
@@ -222,36 +237,36 @@ impl Element {
         match local_name.as_slice() {
             "style" => {
                 let doc = self.node.owner_doc();
-                let base_url = doc.document().url.clone();
+                let base_url = doc.get().extra.url.clone();
                 self.style_attribute = Some(style::parse_style_attribute(value, &base_url))
             }
-            "id" if abstract_self.is_in_doc() => {
-                // XXX: this dual declaration are workaround to avoid the compile error:
-                // "borrowed value does not live long enough"
-                let doc = self.node.owner_doc();
-                let doc = doc.mut_document();
-                doc.update_idmap(abstract_self, Some(value.clone()), old_value);
+            "id" => {
+                let self_node: JS<Node> = NodeCast::from(abstract_self);
+                if self_node.is_in_doc() {
+                    // XXX: this dual declaration are workaround to avoid the compile error:
+                    // "borrowed value does not live long enough"
+                    let mut doc = self.node.owner_doc();
+                    let doc = doc.get_mut();
+                    doc.update_idmap(abstract_self, Some(value.clone()), old_value);
+                }
             }
             _ => ()
         }
 
         //XXXjdm We really need something like a vtable so we can call AfterSetAttr.
         //       This hardcoding is awful.
-        match abstract_self.type_id() {
+        match abstract_self.get().node.type_id {
             ElementNodeTypeId(HTMLImageElementTypeId) => {
-                abstract_self.with_mut_image_element(|image| {
-                    image.AfterSetAttr(local_name.clone(), value.clone());
-                });
+                let mut elem: JS<HTMLImageElement> = HTMLImageElementCast::to(abstract_self);
+                elem.get_mut().AfterSetAttr(local_name.clone(), value.clone());
             }
             ElementNodeTypeId(HTMLIframeElementTypeId) => {
-                abstract_self.with_mut_iframe_element(|iframe| {
-                    iframe.AfterSetAttr(local_name.clone(), value.clone());
-                });
+                let mut elem: JS<HTMLIFrameElement> = HTMLIFrameElementCast::to(abstract_self);
+                elem.get_mut().AfterSetAttr(local_name.clone(), value.clone());
             }
             ElementNodeTypeId(HTMLObjectElementTypeId) => {
-                abstract_self.with_mut_object_element(|object| {
-                    object.AfterSetAttr(local_name.clone(), value.clone());
-                });
+                let mut elem: JS<HTMLObjectElement> = HTMLObjectElementCast::to(abstract_self);
+                elem.get_mut().AfterSetAttr(local_name.clone(), value.clone());
             }
             _ => ()
         }
@@ -260,22 +275,22 @@ impl Element {
     }
 
     pub fn remove_attribute(&mut self,
-                            abstract_self: AbstractNode,
+                            abstract_self: &JS<Element>,
                             namespace: Namespace,
                             name: DOMString) -> ErrorResult {
         let (_, local_name) = get_attribute_parts(name.clone());
 
         self.node.wait_until_safe_to_modify_dom();
 
-        let idx = self.attrs.iter().position(|attr: &@mut Attr| -> bool {
-            attr.local_name == local_name
+        let idx = self.attrs.iter().position(|attr: &JS<Attr>| -> bool {
+            attr.get().local_name == local_name
         });
 
         match idx {
             None => (),
             Some(idx) => {
                 let removed = self.attrs.remove(idx);
-                let removed_raw_value = Some(removed.Value());
+                let removed_raw_value = Some(removed.get().Value());
 
                 if namespace == namespace::Null {
                     self.after_remove_attr(abstract_self, local_name, removed_raw_value);
@@ -287,35 +302,36 @@ impl Element {
     }
 
     fn after_remove_attr(&mut self,
-                         abstract_self: AbstractNode,
+                         abstract_self: &JS<Element>,
                          local_name: DOMString,
                          old_value: Option<DOMString>) {
         match local_name.as_slice() {
             "style" => {
                 self.style_attribute = None
             }
-            "id" if abstract_self.is_in_doc() => {
-                // XXX: this dual declaration are workaround to avoid the compile error:
-                // "borrowed value does not live long enough"
-                let doc = self.node.owner_doc();
-                let doc = doc.mut_document();
-                doc.update_idmap(abstract_self, None, old_value);
+            "id" => {
+                let self_node: JS<Node> = NodeCast::from(abstract_self);
+                if self_node.is_in_doc() {
+                    // XXX: this dual declaration are workaround to avoid the compile error:
+                    // "borrowed value does not live long enough"
+                    let mut doc = self.node.owner_doc();
+                    let doc = doc.get_mut();
+                    doc.update_idmap(abstract_self, None, old_value);
+                }
             }
             _ => ()
         }
 
         //XXXjdm We really need something like a vtable so we can call AfterSetAttr.
         //       This hardcoding is awful.
-        match abstract_self.type_id() {
+        match abstract_self.get().node.type_id {
             ElementNodeTypeId(HTMLImageElementTypeId) => {
-                abstract_self.with_mut_image_element(|image| {
-                    image.AfterRemoveAttr(local_name.clone());
-                });
+                let mut elem: JS<HTMLImageElement> = HTMLImageElementCast::to(abstract_self);
+                elem.get_mut().AfterRemoveAttr(local_name.clone());
             }
             ElementNodeTypeId(HTMLIframeElementTypeId) => {
-                abstract_self.with_mut_iframe_element(|iframe| {
-                    iframe.AfterRemoveAttr(local_name.clone());
-                });
+                let mut elem: JS<HTMLIFrameElement> = HTMLIFrameElementCast::to(abstract_self);
+                elem.get_mut().AfterRemoveAttr(local_name.clone());
             }
             _ => ()
         }
@@ -324,15 +340,16 @@ impl Element {
     }
 
     fn notify_attribute_changed(&self,
-                                abstract_self: AbstractNode,
+                                abstract_self: &JS<Element>,
                                 local_name: DOMString) {
-        if abstract_self.is_in_doc() {
+        let node: JS<Node> = NodeCast::from(abstract_self);
+        if node.is_in_doc() {
             let damage = match local_name.as_slice() {
                 "style" | "id" | "class" => MatchSelectorsDocumentDamage,
                 _ => ContentChangedDocumentDamage
             };
             let document = self.node.owner_doc();
-            document.document().damage_and_reflow(damage);
+            document.get().damage_and_reflow(damage);
         }
     }
 
@@ -357,18 +374,18 @@ impl Element {
         // XXX Resolve URL.
         self.get_string_attribute(name)
     }
-    pub fn set_url_attribute(&mut self, abstract_self: AbstractNode,
+    pub fn set_url_attribute(&mut self, abstract_self: &JS<Element>,
                              name: &str, value: DOMString) {
         self.set_string_attribute(abstract_self, name, value);
     }
 
     pub fn get_string_attribute(&self, name: &str) -> DOMString {
         match self.get_attribute(Null, name) {
-            Some(x) => x.Value(),
+            Some(x) => x.get().Value(),
             None => ~""
         }
     }
-    pub fn set_string_attribute(&mut self, abstract_self: AbstractNode,
+    pub fn set_string_attribute(&mut self, abstract_self: &JS<Element>,
                                 name: &str, value: DOMString) {
         assert!(name == name.to_ascii_lower());
         self.set_attribute(abstract_self, Null, name.to_owned(), value);
@@ -382,25 +399,26 @@ impl Element {
     }
 
     // http://dom.spec.whatwg.org/#dom-element-id
-    pub fn Id(&self, _abstract_self: AbstractNode) -> DOMString {
+    pub fn Id(&self, _abstract_self: &JS<Element>) -> DOMString {
         self.get_string_attribute("id")
     }
 
     // http://dom.spec.whatwg.org/#dom-element-id
-    pub fn SetId(&mut self, abstract_self: AbstractNode, id: DOMString) {
+    pub fn SetId(&mut self, abstract_self: &JS<Element>, id: DOMString) {
         self.set_string_attribute(abstract_self, "id", id);
     }
 
     // http://dom.spec.whatwg.org/#dom-element-attributes
-    pub fn Attributes(&mut self, abstract_self: AbstractNode) -> @mut AttrList {
+    pub fn Attributes(&mut self, abstract_self: &JS<Element>) -> JS<AttrList> {
         match self.attr_list {
             None => {
-                let window = self.node.owner_doc().document().window;
-                let list = AttrList::new(window, abstract_self);
-                self.attr_list = Some(list);
+                let doc = self.node.owner_doc();
+                let doc = doc.get();
+                let list = AttrList::new(&doc.window, abstract_self);
+                self.attr_list = Some(list.clone());
                 list
             }
-            Some(list) => list
+            Some(ref list) => list.clone()
         }
     }
 
@@ -411,18 +429,18 @@ impl Element {
         } else {
             name
         };
-        self.get_attribute(Null, name).map(|s| s.Value())
+        self.get_attribute(Null, name).map(|s| s.get().Value())
     }
 
     // http://dom.spec.whatwg.org/#dom-element-getattributens
     pub fn GetAttributeNS(&self, namespace: Option<DOMString>, local_name: DOMString) -> Option<DOMString> {
         let namespace = Namespace::from_str(null_str_as_empty_ref(&namespace));
         self.get_attribute(namespace, local_name)
-            .map(|attr| attr.value.clone())
+            .map(|attr| attr.get().value.clone())
     }
 
     // http://dom.spec.whatwg.org/#dom-element-setattribute
-    pub fn SetAttribute(&mut self, abstract_self: AbstractNode, name: DOMString, value: DOMString)
+    pub fn SetAttribute(&mut self, abstract_self: &JS<Element>, name: DOMString, value: DOMString)
                         -> ErrorResult {
         // FIXME: If name does not match the Name production in XML, throw an "InvalidCharacterError" exception.
         let name = if self.html_element_in_html_document() {
@@ -435,7 +453,7 @@ impl Element {
 
     // http://dom.spec.whatwg.org/#dom-element-setattributens
     pub fn SetAttributeNS(&mut self,
-                          abstract_self: AbstractNode,
+                          abstract_self: &JS<Element>,
                           namespace_url: Option<DOMString>,
                           name: DOMString,
                           value: DOMString) -> ErrorResult {
@@ -452,7 +470,7 @@ impl Element {
 
     // http://dom.spec.whatwg.org/#dom-element-removeattribute
     pub fn RemoveAttribute(&mut self,
-                           abstract_self: AbstractNode,
+                           abstract_self: &JS<Element>,
                            name: DOMString) -> ErrorResult {
         let name = if self.html_element_in_html_document() {
             name.to_ascii_lower()
@@ -464,7 +482,7 @@ impl Element {
 
     // http://dom.spec.whatwg.org/#dom-element-removeattributens
     pub fn RemoveAttributeNS(&mut self,
-                             abstract_self: AbstractNode,
+                             abstract_self: &JS<Element>,
                              namespace: Option<DOMString>,
                              localname: DOMString) -> ErrorResult {
         let namespace = Namespace::from_str(null_str_as_empty_ref(&namespace));
@@ -482,21 +500,24 @@ impl Element {
     }
 
     // http://dom.spec.whatwg.org/#dom-element-getelementsbytagname
-    pub fn GetElementsByTagName(&self, _localname: DOMString) -> @mut HTMLCollection {
+    pub fn GetElementsByTagName(&self, _localname: DOMString) -> JS<HTMLCollection> {
         // FIXME: stub - https://github.com/mozilla/servo/issues/1660
-        HTMLCollection::new(self.node.owner_doc().document().window, ~[])
+        let doc = self.node.owner_doc();
+        HTMLCollection::new(&doc.get().window, ~[])
     }
 
     // http://dom.spec.whatwg.org/#dom-element-getelementsbytagnamens
-    pub fn GetElementsByTagNameNS(&self, _namespace: Option<DOMString>, _localname: DOMString) -> Fallible<@mut HTMLCollection> {
+    pub fn GetElementsByTagNameNS(&self, _namespace: Option<DOMString>, _localname: DOMString) -> Fallible<JS<HTMLCollection>> {
         // FIXME: stub - https://github.com/mozilla/servo/issues/1660
-        Ok(HTMLCollection::new(self.node.owner_doc().document().window, ~[]))
+        let doc = self.node.owner_doc();
+        Ok(HTMLCollection::new(&doc.get().window, ~[]))
     }
 
     // http://dom.spec.whatwg.org/#dom-element-getelementsbyclassname
-    pub fn GetElementsByClassName(&self, _names: DOMString) -> @mut HTMLCollection {
+    pub fn GetElementsByClassName(&self, _names: DOMString) -> JS<HTMLCollection> {
         // FIXME: stub - https://github.com/mozilla/servo/issues/1660
-        HTMLCollection::new(self.node.owner_doc().document().window, ~[])
+        let doc = self.node.owner_doc();
+        HTMLCollection::new(&doc.get().window, ~[])
     }
 
     // http://dom.spec.whatwg.org/#dom-element-matches
@@ -517,13 +538,14 @@ impl Element {
     pub fn MozRequestPointerLock(&self) {
     }
 
-    pub fn GetClientRects(&self, abstract_self: AbstractNode) -> @mut ClientRectList {
-        let win = self.node.owner_doc().document().window;
-        let node = abstract_self;
-        assert!(node.is_element());
+    pub fn GetClientRects(&self, abstract_self: &JS<Element>) -> JS<ClientRectList> {
+        let doc = self.node.owner_doc();
+        let win = &doc.get().window;
+        let node: JS<Node> = NodeCast::from(abstract_self);
         let (port, chan) = Chan::new();
+        let addr = node.to_trusted_node_address();
         let rects =
-            match win.page.query_layout(ContentBoxesQuery(node, chan), port) {
+            match win.get().page.query_layout(ContentBoxesQuery(addr, chan), port) {
                 ContentBoxesResponse(rects) => {
                     rects.map(|r| {
                         ClientRect::new(
@@ -539,12 +561,13 @@ impl Element {
         ClientRectList::new(win, rects)
     }
 
-    pub fn GetBoundingClientRect(&self, abstract_self: AbstractNode) -> @mut ClientRect {
-        let win = self.node.owner_doc().document().window;
-        let node = abstract_self;
-        assert!(node.is_element());
+    pub fn GetBoundingClientRect(&self, abstract_self: &JS<Element>) -> JS<ClientRect> {
+        let doc = self.node.owner_doc();
+        let win = &doc.get().window;
+        let node: JS<Node> = NodeCast::from(abstract_self);
         let (port, chan) = Chan::new();
-        match win.page.query_layout(ContentBoxQuery(node, chan), port) {
+        let addr = node.to_trusted_node_address();
+        match win.get().page.query_layout(ContentBoxQuery(addr, chan), port) {
             ContentBoxResponse(rect) => {
                 ClientRect::new(
                     win,
@@ -597,20 +620,20 @@ impl Element {
         0
     }
 
-    pub fn GetInnerHTML(&self, abstract_self: AbstractNode) -> Fallible<DOMString> {
+    pub fn GetInnerHTML(&self, abstract_self: &JS<Element>) -> Fallible<DOMString> {
         //XXX TODO: XML case
-        Ok(serialize(&mut NodeIterator::new(abstract_self, false, false)))
+        Ok(serialize(&mut NodeIterator::new(NodeCast::from(abstract_self), false, false)))
     }
 
-    pub fn SetInnerHTML(&mut self, _abstract_self: AbstractNode, _value: DOMString) -> ErrorResult {
+    pub fn SetInnerHTML(&mut self, _abstract_self: &JS<Element>, _value: DOMString) -> ErrorResult {
         Ok(())
     }
 
-    pub fn GetOuterHTML(&self, abstract_self:AbstractNode) -> Fallible<DOMString> {
-        Ok(serialize(&mut NodeIterator::new(abstract_self, true, false)))
+    pub fn GetOuterHTML(&self, abstract_self: &JS<Element>) -> Fallible<DOMString> {
+        Ok(serialize(&mut NodeIterator::new(NodeCast::from(abstract_self), true, false)))
     }
 
-    pub fn SetOuterHTML(&mut self, _abstract_self: AbstractNode, _value: DOMString) -> ErrorResult {
+    pub fn SetOuterHTML(&mut self, _abstract_self: &JS<Element>, _value: DOMString) -> ErrorResult {
         Ok(())
     }
 
@@ -618,7 +641,7 @@ impl Element {
         Ok(())
     }
 
-    pub fn QuerySelector(&self, _selectors: DOMString) -> Fallible<Option<AbstractNode>> {
+    pub fn QuerySelector(&self, _selectors: DOMString) -> Fallible<Option<JS<Element>>> {
         Ok(None)
     }
 }
diff --git a/src/components/script/dom/event.rs b/src/components/script/dom/event.rs
index aef1b4270cd..a8fac4308ef 100644
--- a/src/components/script/dom/event.rs
+++ b/src/components/script/dom/event.rs
@@ -2,20 +2,16 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use dom::eventtarget::AbstractEventTarget;
-use dom::window::Window;
 use dom::bindings::codegen::EventBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::utils::{Fallible, ErrorResult};
-use dom::mouseevent::MouseEvent;
-use dom::uievent::UIEvent;
+use dom::eventtarget::EventTarget;
+use dom::window::Window;
 use servo_util::str::DOMString;
 
 use geom::point::Point2D;
 
-use std::cast;
-use std::unstable::raw::Box;
-
 pub enum Event_ {
     ResizeEvent(uint, uint), 
     ReflowEvent,
@@ -25,10 +21,7 @@ pub enum Event_ {
     MouseMoveEvent(Point2D<f32>)
 }
 
-pub struct AbstractEvent {
-    event: *mut Box<Event>
-}
-
+#[deriving(Encodable)]
 pub enum EventPhase {
     Phase_None = 0,
     Phase_Capturing,
@@ -36,91 +29,7 @@ pub enum EventPhase {
     Phase_Bubbling
 }
 
-impl AbstractEvent {
-    pub fn from_box(box_: *mut Box<Event>) -> AbstractEvent {
-        AbstractEvent {
-            event: box_
-        }
-    }
-
-    //
-    // Downcasting borrows
-    //
-
-    fn transmute<'a, T>(&'a self) -> &'a T {
-        unsafe {
-            let box_: *Box<T> = self.event as *Box<T>;
-            &(*box_).data
-        }
-    }
-
-    fn transmute_mut<'a, T>(&'a self) -> &'a mut T {
-        unsafe {
-            let box_: *mut Box<T> = self.event as *mut Box<T>;
-            &mut (*box_).data
-        }
-    }
-
-    pub fn type_id(&self) -> EventTypeId {
-        self.event().type_id
-    }
-
-    pub fn event<'a>(&'a self) -> &'a Event {
-        self.transmute()
-    }
-
-    pub fn mut_event<'a>(&'a self) -> &'a mut Event {
-        self.transmute_mut()
-    }
-
-    pub fn is_uievent(&self) -> bool {
-        self.type_id() == UIEventTypeId
-    }
-
-    pub fn uievent<'a>(&'a self) -> &'a UIEvent {
-        assert!(self.is_uievent());
-        self.transmute()
-    }
-
-    pub fn mut_uievent<'a>(&'a self) -> &'a mut UIEvent {
-        assert!(self.is_uievent());
-        self.transmute_mut()
-    }
-
-    pub fn is_mouseevent(&self) -> bool {
-        self.type_id() == MouseEventTypeId
-    }
-
-    pub fn mouseevent<'a>(&'a self) -> &'a MouseEvent {
-        assert!(self.is_mouseevent());
-        self.transmute()
-    }
-
-    pub fn mut_mouseevent<'a>(&'a self) -> &'a mut MouseEvent {
-        assert!(self.is_mouseevent());
-        self.transmute_mut()
-    }
-
-    pub fn propagation_stopped(&self) -> bool {
-        self.event().stop_propagation
-    }
-
-    pub fn bubbles(&self) -> bool {
-        self.event().bubbles
-    }
-}
-
-impl Reflectable for AbstractEvent {
-    fn reflector<'a>(&'a self) -> &'a Reflector {
-        self.event().reflector()
-    }
-
-    fn mut_reflector<'a>(&'a mut self) -> &'a mut Reflector {
-        self.mut_event().mut_reflector()
-    }
-}
-
-#[deriving(Eq)]
+#[deriving(Eq, Encodable)]
 pub enum EventTypeId {
     HTMLEventTypeId,
     UIEventTypeId,
@@ -128,11 +37,12 @@ pub enum EventTypeId {
     KeyEventTypeId
 }
 
+#[deriving(Encodable)]
 pub struct Event {
     type_id: EventTypeId,
     reflector_: Reflector,
-    current_target: Option<AbstractEventTarget>,
-    target: Option<AbstractEventTarget>,
+    current_target: Option<JS<EventTarget>>,
+    target: Option<JS<EventTarget>>,
     type_: DOMString,
     phase: EventPhase,
     default_prevented: bool,
@@ -142,7 +52,7 @@ pub struct Event {
     bubbles: bool,
     trusted: bool,
     dispatching: bool,
-    initialized: bool
+    initialized: bool,
 }
 
 impl Event {
@@ -165,18 +75,10 @@ impl Event {
         }
     }
 
-    //FIXME: E should be bounded by some trait that is only implemented for Event types
-    pub fn as_abstract<E>(event: @mut E) -> AbstractEvent {
-        // This surrenders memory management of the event!
-        AbstractEvent {
-            event: unsafe { cast::transmute(event) },
-        }
-    }
-
-    pub fn new(window: @mut Window) -> AbstractEvent {
-        let ev = reflect_dom_object(@mut Event::new_inherited(HTMLEventTypeId),
-                                    window, EventBinding::Wrap);
-        Event::as_abstract(ev)
+    pub fn new(window: &JS<Window>) -> JS<Event> {
+        reflect_dom_object(~Event::new_inherited(HTMLEventTypeId),
+                           window.get(),
+                           EventBinding::Wrap)
     }
 
     pub fn EventPhase(&self) -> u16 {
@@ -187,12 +89,12 @@ impl Event {
         self.type_.clone()
     }
 
-    pub fn GetTarget(&self) -> Option<AbstractEventTarget> {
-        self.target
+    pub fn GetTarget(&self) -> Option<JS<EventTarget>> {
+        self.target.clone()
     }
 
-    pub fn GetCurrentTarget(&self) -> Option<AbstractEventTarget> {
-        self.current_target
+    pub fn GetCurrentTarget(&self) -> Option<JS<EventTarget>> {
+        self.current_target.clone()
     }
 
     pub fn DefaultPrevented(&self) -> bool {
@@ -241,11 +143,11 @@ impl Event {
         self.trusted
     }
 
-    pub fn Constructor(global: @mut Window,
+    pub fn Constructor(global: &JS<Window>,
                        type_: DOMString,
-                       init: &EventBinding::EventInit) -> Fallible<AbstractEvent> {
-        let ev = Event::new(global);
-        ev.mut_event().InitEvent(type_, init.bubbles, init.cancelable);
+                       init: &EventBinding::EventInit) -> Fallible<JS<Event>> {
+        let mut ev = Event::new(global);
+        ev.get_mut().InitEvent(type_, init.bubbles, init.cancelable);
         Ok(ev)
     }
 }
diff --git a/src/components/script/dom/eventdispatcher.rs b/src/components/script/dom/eventdispatcher.rs
index 5a1c09ce9f6..c22ef7716c1 100644
--- a/src/components/script/dom/eventdispatcher.rs
+++ b/src/components/script/dom/eventdispatcher.rs
@@ -3,50 +3,57 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::callback::eReportExceptions;
-use dom::eventtarget::{AbstractEventTarget, Capturing, Bubbling};
-use dom::event::{AbstractEvent, Phase_At_Target, Phase_None, Phase_Bubbling, Phase_Capturing};
-use dom::node::AbstractNode;
+use dom::bindings::codegen::InheritTypes::{EventTargetCast, NodeCast, NodeDerived};
+use dom::bindings::js::JS;
+use dom::eventtarget::{Capturing, Bubbling, EventTarget};
+use dom::event::{Event, Phase_At_Target, Phase_None, Phase_Bubbling, Phase_Capturing};
+use dom::node::{Node, NodeHelpers};
 
 // See http://dom.spec.whatwg.org/#concept-event-dispatch for the full dispatch algorithm
-pub fn dispatch_event(target: AbstractEventTarget,
-                      pseudo_target: Option<AbstractEventTarget>,
-                      event: AbstractEvent) -> bool {
-    assert!(!event.event().dispatching);
+pub fn dispatch_event(target: &JS<EventTarget>,
+                      pseudo_target: Option<JS<EventTarget>>,
+                      event: &mut JS<Event>) -> bool {
+    assert!(!event.get().dispatching);
 
     {
-        let event = event.mut_event();
-        event.target = Some(pseudo_target.unwrap_or(target));
+        let event = event.get_mut();
+        event.target = match pseudo_target {
+            Some(pseudo_target) => Some(pseudo_target),
+            None => Some(target.clone())
+        };
         event.dispatching = true;
     }
 
-    let type_ = event.event().type_.clone();
+    let type_ = event.get().type_.clone();
     let mut chain = ~[];
 
     //TODO: no chain if not participating in a tree
-    if target.is_node() {
-        for ancestor in AbstractNode::from_eventtarget(target).ancestors() {
-            chain.push(AbstractEventTarget::from_node(ancestor));
+    if target.get().is_node() {
+        let target_node: JS<Node> = NodeCast::to(target);
+        for ancestor in target_node.ancestors() {
+            let ancestor_target: JS<EventTarget> = EventTargetCast::from(&ancestor);
+            chain.push(ancestor_target);
         }
     }
 
-    event.mut_event().phase = Phase_Capturing;
+    event.get_mut().phase = Phase_Capturing;
 
     //FIXME: The "callback this value" should be currentTarget
 
     /* capturing */
-    for &cur_target in chain.rev_iter() {
-        let stopped = match cur_target.eventtarget().get_listeners_for(type_, Capturing) {
+    for cur_target in chain.rev_iter() {
+        let stopped = match cur_target.get().get_listeners_for(type_, Capturing) {
             Some(listeners) => {
-                event.mut_event().current_target = Some(cur_target);
+                event.get_mut().current_target = Some(cur_target.clone());
                 for listener in listeners.iter() {
                     listener.HandleEvent__(event, eReportExceptions);
 
-                    if event.event().stop_immediate {
+                    if event.get().stop_immediate {
                         break;
                     }
                 }
 
-                event.propagation_stopped()
+                event.get().stop_propagation
             }
             None => false
         };
@@ -57,18 +64,18 @@ pub fn dispatch_event(target: AbstractEventTarget,
     }
 
     /* at target */
-    if !event.propagation_stopped() {
+    if !event.get().stop_propagation {
         {
-            let event = event.mut_event();
+            let event = event.get_mut();
             event.phase = Phase_At_Target;
-            event.current_target = Some(target);
+            event.current_target = Some(target.clone());
         }
 
-        let opt_listeners = target.eventtarget().get_listeners(type_);
+        let opt_listeners = target.get().get_listeners(type_);
         for listeners in opt_listeners.iter() {
             for listener in listeners.iter() {
                 listener.HandleEvent__(event, eReportExceptions);
-                if event.event().stop_immediate {
+                if event.get().stop_immediate {
                     break;
                 }
             }
@@ -76,22 +83,22 @@ pub fn dispatch_event(target: AbstractEventTarget,
     }
 
     /* bubbling */
-    if event.bubbles() && !event.propagation_stopped() {
-        event.mut_event().phase = Phase_Bubbling;
+    if event.get().bubbles && !event.get().stop_propagation {
+        event.get_mut().phase = Phase_Bubbling;
 
-        for &cur_target in chain.iter() {
-            let stopped = match cur_target.eventtarget().get_listeners_for(type_, Bubbling) {
+        for cur_target in chain.iter() {
+            let stopped = match cur_target.get().get_listeners_for(type_, Bubbling) {
                 Some(listeners) => {
-                    event.mut_event().current_target = Some(cur_target);
+                    event.get_mut().current_target = Some(cur_target.clone());
                     for listener in listeners.iter() {
                         listener.HandleEvent__(event, eReportExceptions);
 
-                        if event.event().stop_immediate {
+                        if event.get().stop_immediate {
                             break;
                         }
                     }
 
-                    event.propagation_stopped()
+                    event.get().stop_propagation
                 }
                 None => false
             };
@@ -101,7 +108,7 @@ pub fn dispatch_event(target: AbstractEventTarget,
         }
     }
 
-    let event = event.mut_event();
+    let event = event.get_mut();
     event.dispatching = false;
     event.phase = Phase_None;
     event.current_target = None;
diff --git a/src/components/script/dom/eventtarget.rs b/src/components/script/dom/eventtarget.rs
index dbc435ac012..07445b12de5 100644
--- a/src/components/script/dom/eventtarget.rs
+++ b/src/components/script/dom/eventtarget.rs
@@ -2,122 +2,42 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector};
 use dom::bindings::utils::{Fallible, InvalidState};
 use dom::bindings::codegen::EventListenerBinding::EventListener;
-use dom::document::AbstractDocument;
-use dom::event::AbstractEvent;
+use dom::event::Event;
 use dom::eventdispatcher::dispatch_event;
-use dom::node::AbstractNode;
-use dom::window::Window;
+use dom::node::NodeTypeId;
 use servo_util::str::DOMString;
 
-use std::cast;
 use std::hashmap::HashMap;
-use std::unstable::raw::Box;
 
-#[deriving(Eq)]
+#[deriving(Eq,Encodable)]
 pub enum ListenerPhase {
     Capturing,
     Bubbling,
 }
 
-#[deriving(Eq)]
+#[deriving(Eq,Encodable)]
 pub enum EventTargetTypeId {
     WindowTypeId,
-    NodeTypeId
+    NodeTargetTypeId(NodeTypeId)
 }
 
-#[deriving(Eq)]
+#[deriving(Eq,Encodable)]
 struct EventListenerEntry {
     phase: ListenerPhase,
     listener: EventListener
 }
 
+#[deriving(Encodable)]
 pub struct EventTarget {
     type_id: EventTargetTypeId,
     reflector_: Reflector,
     handlers: HashMap<DOMString, ~[EventListenerEntry]>,
 }
 
-pub struct AbstractEventTarget {
-    eventtarget: *mut Box<EventTarget>
-}
-
-impl AbstractEventTarget {
-    pub fn from_box<T>(box_: *mut Box<T>) -> AbstractEventTarget {
-        AbstractEventTarget {
-            eventtarget: box_ as *mut Box<EventTarget>
-        }
-    }
-
-    pub fn from_node(node: AbstractNode) -> AbstractEventTarget {
-        unsafe {
-            cast::transmute(node)
-        }
-    }
-
-    pub fn from_window(window: @mut Window) -> AbstractEventTarget {
-        AbstractEventTarget {
-            eventtarget: unsafe { cast::transmute(window) }
-        }
-    }
-
-    pub fn from_document(document: AbstractDocument) -> AbstractEventTarget {
-        unsafe {
-            cast::transmute(document)
-        }
-    }
-
-    pub fn type_id(&self) -> EventTargetTypeId {
-        self.eventtarget().type_id
-    }
-
-    pub fn is_window(&self) -> bool {
-        self.type_id() == WindowTypeId
-    }
-
-    pub fn is_node(&self) -> bool {
-        self.type_id() == NodeTypeId
-    }
-
-    //
-    // Downcasting borrows
-    //
-
-    fn transmute<'a, T>(&'a self) -> &'a T {
-        unsafe {
-            let box_: *Box<T> = self.eventtarget as *Box<T>;
-            &(*box_).data
-        }
-    }
-
-    fn transmute_mut<'a, T>(&'a mut self) -> &'a mut T {
-        unsafe {
-            let box_: *mut Box<T> = self.eventtarget as *mut Box<T>;
-            &mut (*box_).data
-        }
-    }
-
-    pub fn eventtarget<'a>(&'a self) -> &'a EventTarget {
-        self.transmute()
-    }
-
-    pub fn mut_eventtarget<'a>(&'a mut self) -> &'a mut EventTarget {
-        self.transmute_mut()
-    }
-}
-
-impl Reflectable for AbstractEventTarget {
-    fn reflector<'a>(&'a self) -> &'a Reflector {
-        self.eventtarget().reflector()
-    }
-
-    fn mut_reflector<'a>(&'a mut self) -> &'a mut Reflector {
-        self.mut_eventtarget().mut_reflector()
-    }
-}
-
 impl EventTarget {
     pub fn new_inherited(type_id: EventTargetTypeId) -> EventTarget {
         EventTarget {
@@ -178,15 +98,16 @@ impl EventTarget {
         }
     }
 
-    pub fn DispatchEvent(&self, abstract_self: AbstractEventTarget, event: AbstractEvent) -> Fallible<bool> {
+    pub fn DispatchEvent(&self, abstract_self: &JS<EventTarget>,
+                         event: &mut JS<Event>) -> Fallible<bool> {
         self.dispatch_event_with_target(abstract_self, None, event)
     }
 
     pub fn dispatch_event_with_target(&self,
-                                      abstract_self: AbstractEventTarget,
-                                      abstract_target: Option<AbstractEventTarget>,
-                                      event: AbstractEvent) -> Fallible<bool> {
-        if event.event().dispatching || !event.event().initialized {
+                                      abstract_self: &JS<EventTarget>,
+                                      abstract_target: Option<JS<EventTarget>>,
+                                      event: &mut JS<Event>) -> Fallible<bool> {
+        if event.get().dispatching || !event.get().initialized {
             return Err(InvalidState);
         }
         Ok(dispatch_event(abstract_self, abstract_target, event))
diff --git a/src/components/script/dom/formdata.rs b/src/components/script/dom/formdata.rs
index b446c44a7d7..3beb7e996aa 100644
--- a/src/components/script/dom/formdata.rs
+++ b/src/components/script/dom/formdata.rs
@@ -4,27 +4,30 @@
 
 use dom::bindings::utils::{Fallible, Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::codegen::FormDataBinding;
+use dom::bindings::js::JS;
 use dom::blob::Blob;
-use dom::node::AbstractNode;
+use dom::htmlformelement::HTMLFormElement;
 use dom::window::Window;
 use servo_util::str::DOMString;
 
 use std::hashmap::HashMap;
 
+#[deriving(Encodable)]
 enum FormDatum {
     StringData(DOMString),
-    BlobData { blob: @mut Blob, name: DOMString }
+    BlobData { blob: JS<Blob>, name: DOMString }
 }
 
+#[deriving(Encodable)]
 pub struct FormData {
     data: HashMap<DOMString, FormDatum>,
     reflector_: Reflector,
-    window: @mut Window,
-    form: Option<AbstractNode>
+    window: JS<Window>,
+    form: Option<JS<HTMLFormElement>>
 }
 
 impl FormData {
-    pub fn new_inherited(form: Option<AbstractNode>, window: @mut Window) -> FormData {
+    pub fn new_inherited(form: Option<JS<HTMLFormElement>>, window: JS<Window>) -> FormData {
         FormData {
             data: HashMap::new(),
             reflector_: Reflector::new(),
@@ -33,18 +36,18 @@ impl FormData {
         }
     }
 
-    pub fn new(form: Option<AbstractNode>, window: @mut Window) -> @mut FormData {
-        reflect_dom_object(@mut FormData::new_inherited(form, window), window, FormDataBinding::Wrap)
+    pub fn new(form: Option<JS<HTMLFormElement>>, window: &JS<Window>) -> JS<FormData> {
+        reflect_dom_object(~FormData::new_inherited(form, window.clone()), window.get(), FormDataBinding::Wrap)
     }
 
-    pub fn Constructor(window: @mut Window, form: Option<AbstractNode>)
-                       -> Fallible<@mut FormData> {
+    pub fn Constructor(window: &JS<Window>, form: Option<JS<HTMLFormElement>>)
+                       -> Fallible<JS<FormData>> {
         Ok(FormData::new(form, window))
     }
 
-    pub fn Append(&mut self, name: DOMString, value: @mut Blob, filename: Option<DOMString>) {
+    pub fn Append(&mut self, name: DOMString, value: &JS<Blob>, filename: Option<DOMString>) {
         let blob = BlobData {
-            blob: value,
+            blob: value.clone(),
             name: filename.unwrap_or(~"default")
         };
         self.data.insert(name.clone(), blob);
diff --git a/src/components/script/dom/htmlanchorelement.rs b/src/components/script/dom/htmlanchorelement.rs
index d398a8cbe03..4b4bcf7c115 100644
--- a/src/components/script/dom/htmlanchorelement.rs
+++ b/src/components/script/dom/htmlanchorelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLAnchorElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLAnchorElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLAnchorElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLAnchorElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLAnchorElementDerived for EventTarget {
+    fn is_htmlanchorelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLAnchorElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLAnchorElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLAnchorElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLAnchorElement {
         HTMLAnchorElement {
             htmlelement: HTMLElement::new_inherited(HTMLAnchorElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLAnchorElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLAnchorElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLAnchorElement> {
+        let element = HTMLAnchorElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLAnchorElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlappletelement.rs b/src/components/script/dom/htmlappletelement.rs
index babaeaaf1f0..463414890c8 100644
--- a/src/components/script/dom/htmlappletelement.rs
+++ b/src/components/script/dom/htmlappletelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLAppletElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLAppletElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLAppletElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLAppletElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLAppletElementDerived for EventTarget {
+    fn is_htmlappletelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLAppletElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLAppletElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLAppletElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLAppletElement {
         HTMLAppletElement {
             htmlelement: HTMLElement::new_inherited(HTMLAppletElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLAppletElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLAppletElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLAppletElement> {
+        let element = HTMLAppletElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLAppletElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlareaelement.rs b/src/components/script/dom/htmlareaelement.rs
index 3d80090d2c4..91d89feed00 100644
--- a/src/components/script/dom/htmlareaelement.rs
+++ b/src/components/script/dom/htmlareaelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLAreaElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLAreaElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLAreaElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLAreaElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLAreaElementDerived for EventTarget {
+    fn is_htmlareaelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLAreaElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLAreaElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLAreaElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLAreaElement {
         HTMLAreaElement {
             htmlelement: HTMLElement::new_inherited(HTMLAreaElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLAreaElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLAreaElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLAreaElement> {
+        let element = HTMLAreaElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLAreaElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlaudioelement.rs b/src/components/script/dom/htmlaudioelement.rs
index 6e753318cb7..0575d3a49f2 100644
--- a/src/components/script/dom/htmlaudioelement.rs
+++ b/src/components/script/dom/htmlaudioelement.rs
@@ -3,25 +3,38 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLAudioElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLAudioElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLAudioElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlmediaelement::HTMLMediaElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLAudioElement {
     htmlmediaelement: HTMLMediaElement
 }
 
+impl HTMLAudioElementDerived for EventTarget {
+    fn is_htmlaudioelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLAudioElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLAudioElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLAudioElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLAudioElement {
         HTMLAudioElement {
             htmlmediaelement: HTMLMediaElement::new_inherited(HTMLAudioElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLAudioElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLAudioElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLAudioElement> {
+        let element = HTMLAudioElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLAudioElementBinding::Wrap)
     }
 }
diff --git a/src/components/script/dom/htmlbaseelement.rs b/src/components/script/dom/htmlbaseelement.rs
index cf71f76dfbd..4384d620e93 100644
--- a/src/components/script/dom/htmlbaseelement.rs
+++ b/src/components/script/dom/htmlbaseelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLBaseElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLBaseElementDerived;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLBaseElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLBaseElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLBaseElementDerived for EventTarget {
+    fn is_htmlbaseelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLBaseElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLBaseElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLBaseElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLBaseElement {
         HTMLBaseElement {
             htmlelement: HTMLElement::new_inherited(HTMLBaseElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLBaseElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLBaseElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLBaseElement> {
+        let element = HTMLBaseElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLBaseElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlbodyelement.rs b/src/components/script/dom/htmlbodyelement.rs
index 32d133f6760..a12a0dcf68f 100644
--- a/src/components/script/dom/htmlbodyelement.rs
+++ b/src/components/script/dom/htmlbodyelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLBodyElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLBodyElementDerived;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLBodyElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLBodyElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLBodyElementDerived for EventTarget {
+    fn is_htmlbodyelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLBodyElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLBodyElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLBodyElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLBodyElement {
         HTMLBodyElement {
             htmlelement: HTMLElement::new_inherited(HTMLBodyElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLBodyElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLBodyElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLBodyElement> {
+        let element = HTMLBodyElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLBodyElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlbrelement.rs b/src/components/script/dom/htmlbrelement.rs
index 67462d28abb..9da6651455d 100644
--- a/src/components/script/dom/htmlbrelement.rs
+++ b/src/components/script/dom/htmlbrelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLBRElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLBRElementDerived;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLBRElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLBRElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLBRElementDerived for EventTarget {
+    fn is_htmlbrelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLBRElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLBRElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLBRElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLBRElement {
         HTMLBRElement {
             htmlelement: HTMLElement::new_inherited(HTMLBRElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLBRElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLBRElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLBRElement> {
+        let element = HTMLBRElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLBRElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlbuttonelement.rs b/src/components/script/dom/htmlbuttonelement.rs
index 4847ce12394..83662da0340 100644
--- a/src/components/script/dom/htmlbuttonelement.rs
+++ b/src/components/script/dom/htmlbuttonelement.rs
@@ -3,28 +3,42 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLButtonElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLButtonElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLButtonElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::htmlformelement::HTMLFormElement;
+use dom::node::{Node, ElementNodeTypeId};
 use dom::validitystate::ValidityState;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLButtonElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLButtonElementDerived for EventTarget {
+    fn is_htmlbuttonelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLButtonElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLButtonElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLButtonElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLButtonElement {
         HTMLButtonElement {
             htmlelement: HTMLElement::new_inherited(HTMLButtonElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLButtonElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLButtonElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLButtonElement> {
+        let element = HTMLButtonElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLButtonElementBinding::Wrap)
     }
 }
 
@@ -45,7 +59,7 @@ impl HTMLButtonElement {
         Ok(())
     }
 
-    pub fn GetForm(&self) -> Option<AbstractNode> {
+    pub fn GetForm(&self) -> Option<JS<HTMLFormElement>> {
         None
     }
 
@@ -120,12 +134,13 @@ impl HTMLButtonElement {
     pub fn SetWillValidate(&mut self, _will_validate: bool) {
     }
 
-    pub fn Validity(&self) -> @mut ValidityState {
-        let global = self.htmlelement.element.node.owner_doc().document().window;
-        ValidityState::new(global)
+    pub fn Validity(&self) -> JS<ValidityState> {
+        let doc = self.htmlelement.element.node.owner_doc();
+        let doc = doc.get();
+        ValidityState::new(&doc.window)
     }
 
-    pub fn SetValidity(&mut self, _validity: @mut ValidityState) {
+    pub fn SetValidity(&mut self, _validity: JS<ValidityState>) {
     }
 
     pub fn ValidationMessage(&self) -> DOMString {
diff --git a/src/components/script/dom/htmlcanvaselement.rs b/src/components/script/dom/htmlcanvaselement.rs
index dcc75ea73f1..199f4ad8c5b 100644
--- a/src/components/script/dom/htmlcanvaselement.rs
+++ b/src/components/script/dom/htmlcanvaselement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLCanvasElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLCanvasElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{ErrorResult};
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLCanvasElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLCanvasElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLCanvasElementDerived for EventTarget {
+    fn is_htmlcanvaselement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLCanvasElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLCanvasElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLCanvasElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLCanvasElement {
         HTMLCanvasElement {
             htmlelement: HTMLElement::new_inherited(HTMLCanvasElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLCanvasElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLCanvasElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLCanvasElement> {
+        let element = HTMLCanvasElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLCanvasElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlcollection.rs b/src/components/script/dom/htmlcollection.rs
index 32cdd52280c..f14ecd05db7 100644
--- a/src/components/script/dom/htmlcollection.rs
+++ b/src/components/script/dom/htmlcollection.rs
@@ -3,9 +3,10 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLCollectionBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::utils::Fallible;
-use dom::node::AbstractNode;
+use dom::element::Element;
 use dom::window::Window;
 use servo_util::str::DOMString;
 
@@ -13,14 +14,15 @@ use js::jsapi::{JSObject, JSContext};
 
 use std::ptr;
 
+#[deriving(Encodable)]
 pub struct HTMLCollection {
-    elements: ~[AbstractNode],
+    elements: ~[JS<Element>],
     reflector_: Reflector,
-    window: @mut Window,
+    window: JS<Window>,
 }
 
 impl HTMLCollection {
-    pub fn new_inherited(window: @mut Window, elements: ~[AbstractNode]) -> HTMLCollection {
+    pub fn new_inherited(window: JS<Window>, elements: ~[JS<Element>]) -> HTMLCollection {
         HTMLCollection {
             elements: elements,
             reflector_: Reflector::new(),
@@ -28,18 +30,18 @@ impl HTMLCollection {
         }
     }
 
-    pub fn new(window: @mut Window, elements: ~[AbstractNode]) -> @mut HTMLCollection {
-        reflect_dom_object(@mut HTMLCollection::new_inherited(window, elements),
-                           window, HTMLCollectionBinding::Wrap)
+    pub fn new(window: &JS<Window>, elements: ~[JS<Element>]) -> JS<HTMLCollection> {
+        reflect_dom_object(~HTMLCollection::new_inherited(window.clone(), elements),
+                           window.get(), HTMLCollectionBinding::Wrap)
     }
     
     pub fn Length(&self) -> u32 {
         self.elements.len() as u32
     }
 
-    pub fn Item(&self, index: u32) -> Option<AbstractNode> {
+    pub fn Item(&self, index: u32) -> Option<JS<Element>> {
         if index < self.Length() {
-            Some(self.elements[index])
+            Some(self.elements[index].clone())
         } else {
             None
         }
@@ -49,7 +51,7 @@ impl HTMLCollection {
         Ok(ptr::null())
     }
 
-    pub fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<AbstractNode> {
+    pub fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<JS<Element>> {
         *found = true;
         self.Item(index)
     }
diff --git a/src/components/script/dom/htmldataelement.rs b/src/components/script/dom/htmldataelement.rs
index cd8a99bd282..59eb30945c6 100644
--- a/src/components/script/dom/htmldataelement.rs
+++ b/src/components/script/dom/htmldataelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLDataElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLDataElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLDataElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLDataElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLDataElementDerived for EventTarget {
+    fn is_htmldataelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLDataElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLDataElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLDataElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLDataElement {
         HTMLDataElement {
             htmlelement: HTMLElement::new_inherited(HTMLDataElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLDataElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLDataElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLDataElement> {
+        let element = HTMLDataElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLDataElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmldatalistelement.rs b/src/components/script/dom/htmldatalistelement.rs
index 41665545a48..6cd888029c2 100644
--- a/src/components/script/dom/htmldatalistelement.rs
+++ b/src/components/script/dom/htmldatalistelement.rs
@@ -3,33 +3,47 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLDataListElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLDataListElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLDataListElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlcollection::HTMLCollection;
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLDataListElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLDataListElementDerived for EventTarget {
+    fn is_htmldatalistelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLDataListElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLDataListElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLDataListElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLDataListElement {
         HTMLDataListElement {
             htmlelement: HTMLElement::new_inherited(HTMLDataListElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLDataListElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLDataListElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLDataListElement> {
+        let element = HTMLDataListElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLDataListElementBinding::Wrap)
     }
 }
 
 impl HTMLDataListElement {
-    pub fn Options(&self) -> @mut HTMLCollection {
-        let window = self.htmlelement.element.node.owner_doc().document().window;
-        HTMLCollection::new(window, ~[])
+    pub fn Options(&self) -> JS<HTMLCollection> {
+        let doc = self.htmlelement.element.node.owner_doc();
+        let doc = doc.get();
+        HTMLCollection::new(&doc.window, ~[])
     }
 }
diff --git a/src/components/script/dom/htmldirectoryelement.rs b/src/components/script/dom/htmldirectoryelement.rs
index 137aaffd1a2..6847d7b1cf3 100644
--- a/src/components/script/dom/htmldirectoryelement.rs
+++ b/src/components/script/dom/htmldirectoryelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLDirectoryElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLDirectoryElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLDirectoryElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLDirectoryElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLDirectoryElementDerived for EventTarget {
+    fn is_htmldirectoryelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLDirectoryElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLDirectoryElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLDirectoryElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLDirectoryElement {
         HTMLDirectoryElement {
             htmlelement: HTMLElement::new_inherited(HTMLDirectoryElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLDirectoryElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLDirectoryElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLDirectoryElement> {
+        let element = HTMLDirectoryElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLDirectoryElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmldivelement.rs b/src/components/script/dom/htmldivelement.rs
index 3e09183e5bd..3220a7c6e24 100644
--- a/src/components/script/dom/htmldivelement.rs
+++ b/src/components/script/dom/htmldivelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLDivElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLDivElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLDivElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLDivElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLDivElementDerived for EventTarget {
+    fn is_htmldivelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLDivElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLDivElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLDivElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLDivElement {
         HTMLDivElement {
             htmlelement: HTMLElement::new_inherited(HTMLDivElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLDivElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLDivElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLDivElement> {
+        let element = HTMLDivElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLDivElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmldlistelement.rs b/src/components/script/dom/htmldlistelement.rs
index da9576fcb07..c1394c37bd8 100644
--- a/src/components/script/dom/htmldlistelement.rs
+++ b/src/components/script/dom/htmldlistelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLDListElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLDListElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLDListElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLDListElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLDListElementDerived for EventTarget {
+    fn is_htmldlistelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLDListElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLDListElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLDListElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLDListElement {
         HTMLDListElement {
             htmlelement: HTMLElement::new_inherited(HTMLDListElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLDListElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLDListElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLDListElement> {
+        let element = HTMLDListElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLDListElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmldocument.rs b/src/components/script/dom/htmldocument.rs
deleted file mode 100644
index 8297fd3e90c..00000000000
--- a/src/components/script/dom/htmldocument.rs
+++ /dev/null
@@ -1,86 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-use dom::bindings::codegen::HTMLDocumentBinding;
-use dom::bindings::utils::{Reflectable, Reflector, Traceable};
-use dom::document::{AbstractDocument, Document, HTML};
-use dom::htmlcollection::HTMLCollection;
-use dom::window::Window;
-use servo_util::namespace::Null;
-
-use extra::url::Url;
-use js::jsapi::JSTracer;
-
-pub struct HTMLDocument {
-    parent: Document
-}
-
-impl HTMLDocument {
-    pub fn new_inherited(window: @mut Window, url: Option<Url>) -> HTMLDocument {
-        HTMLDocument {
-            parent: Document::new_inherited(window, url, HTML, None)
-        }
-    }
-
-    pub fn new(window: @mut Window, url: Option<Url>) -> AbstractDocument {
-        let document = HTMLDocument::new_inherited(window, url);
-        Document::reflect_document(@mut document, window, HTMLDocumentBinding::Wrap)
-    }
-}
-
-impl HTMLDocument {
-    pub fn Images(&self) -> @mut HTMLCollection {
-        self.parent.createHTMLCollection(|elem| "img" == elem.tag_name)
-    }
-
-    pub fn Embeds(&self) -> @mut HTMLCollection {
-        self.parent.createHTMLCollection(|elem| "embed" == elem.tag_name)
-    }
-
-    pub fn Plugins(&self) -> @mut HTMLCollection {
-        self.Embeds()
-    }
-
-    pub fn Links(&self) -> @mut HTMLCollection {
-        self.parent.createHTMLCollection(|elem| {
-            ("a" == elem.tag_name || "area" == elem.tag_name) &&
-            elem.get_attribute(Null, "href").is_some()
-        })
-    }
-
-    pub fn Forms(&self) -> @mut HTMLCollection {
-        self.parent.createHTMLCollection(|elem| "form" == elem.tag_name)
-    }
-
-    pub fn Scripts(&self) -> @mut HTMLCollection {
-        self.parent.createHTMLCollection(|elem| "script" == elem.tag_name)
-    }
-
-    pub fn Anchors(&self) -> @mut HTMLCollection {
-        self.parent.createHTMLCollection(|elem| {
-            "a" == elem.tag_name && elem.get_attribute(Null, "name").is_some()
-        })
-    }
-
-    pub fn Applets(&self) -> @mut HTMLCollection {
-        // FIXME: This should be return OBJECT elements containing applets.
-        self.parent.createHTMLCollection(|elem| "applet" == elem.tag_name)
-    }
-}
-
-impl Reflectable for HTMLDocument {
-    fn reflector<'a>(&'a self) -> &'a Reflector {
-        self.parent.reflector()
-    }
-
-    fn mut_reflector<'a>(&'a mut self) -> &'a mut Reflector {
-        self.parent.mut_reflector()
-    }
-}
-
-impl Traceable for HTMLDocument {
-    fn trace(&self, tracer: *mut JSTracer) {
-        self.parent.trace(tracer);
-    }
-}
diff --git a/src/components/script/dom/htmlelement.rs b/src/components/script/dom/htmlelement.rs
index 06ab085f945..55c7c1141b6 100644
--- a/src/components/script/dom/htmlelement.rs
+++ b/src/components/script/dom/htmlelement.rs
@@ -3,29 +3,42 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLElementBinding;
-use dom::bindings::utils::{Fallible, ErrorResult};
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLElementDerived;
+use dom::bindings::js::JS;
+use dom::bindings::utils::{ErrorResult, Fallible};
+use dom::document::Document;
 use dom::element::{Element, ElementTypeId, HTMLElementTypeId};
-use dom::node::{AbstractNode, Node};
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::node::{Node, ElementNodeTypeId};
 use js::jsapi::{JSContext, JSVal};
 use js::JSVAL_NULL;
 use servo_util::namespace;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLElement {
     element: Element
 }
 
+impl HTMLElementDerived for EventTarget {
+    fn is_htmlelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(_)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLElement {
-    pub fn new_inherited(type_id: ElementTypeId, tag_name: DOMString, document: AbstractDocument) -> HTMLElement {
+    pub fn new_inherited(type_id: ElementTypeId, tag_name: DOMString, document: JS<Document>) -> HTMLElement {
         HTMLElement {
             element: Element::new_inherited(type_id, tag_name, namespace::HTML, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLElement::new_inherited(HTMLElementTypeId, localName, document);
-        Node::reflect_node(@mut element, document, HTMLElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLElement> {
+        let element = HTMLElement::new_inherited(HTMLElementTypeId, localName, document.clone());
+        Node::reflect_node(~element, document, HTMLElementBinding::Wrap)
     }
 }
 
@@ -134,7 +147,7 @@ impl HTMLElement {
     pub fn SetClassName(&self, _class: DOMString) {
     }
 
-    pub fn GetOffsetParent(&self) -> Option<AbstractNode> {
+    pub fn GetOffsetParent(&self) -> Option<JS<Element>> {
         None
     }
 
diff --git a/src/components/script/dom/htmlembedelement.rs b/src/components/script/dom/htmlembedelement.rs
index a7b5609bfd2..d2da7f540d1 100644
--- a/src/components/script/dom/htmlembedelement.rs
+++ b/src/components/script/dom/htmlembedelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLEmbedElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLEmbedElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLEmbedElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLEmbedElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLEmbedElementDerived for EventTarget {
+    fn is_htmlembedelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLEmbedElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLEmbedElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLEmbedElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLEmbedElement {
         HTMLEmbedElement {
             htmlelement: HTMLElement::new_inherited(HTMLEmbedElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLEmbedElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLEmbedElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLEmbedElement> {
+        let element = HTMLEmbedElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLEmbedElementBinding::Wrap)
     }
 }
 
@@ -76,7 +89,7 @@ impl HTMLEmbedElement {
         Ok(())
     }
 
-    pub fn GetSVGDocument(&self) -> Option<AbstractDocument> {
+    pub fn GetSVGDocument(&self) -> Option<JS<Document>> {
         None
     }
 }
diff --git a/src/components/script/dom/htmlfieldsetelement.rs b/src/components/script/dom/htmlfieldsetelement.rs
index a9939b4c4c9..a67e3a8bc91 100644
--- a/src/components/script/dom/htmlfieldsetelement.rs
+++ b/src/components/script/dom/htmlfieldsetelement.rs
@@ -3,29 +3,43 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLFieldSetElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLFieldSetElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLFieldSetElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::htmlformelement::HTMLFormElement;
 use dom::htmlcollection::HTMLCollection;
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use dom::validitystate::ValidityState;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLFieldSetElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLFieldSetElementDerived for EventTarget {
+    fn is_htmlfieldsetelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLFieldSetElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLFieldSetElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLFieldSetElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLFieldSetElement {
         HTMLFieldSetElement {
             htmlelement: HTMLElement::new_inherited(HTMLFieldSetElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLFieldSetElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLFieldSetElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLFieldSetElement> {
+        let element = HTMLFieldSetElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLFieldSetElementBinding::Wrap)
     }
 }
 
@@ -38,7 +52,7 @@ impl HTMLFieldSetElement {
         Ok(())
     }
 
-    pub fn GetForm(&self) -> Option<AbstractNode> {
+    pub fn GetForm(&self) -> Option<JS<HTMLFormElement>> {
         None
     }
 
@@ -54,18 +68,20 @@ impl HTMLFieldSetElement {
         ~""
     }
 
-    pub fn Elements(&self) -> @mut HTMLCollection {
-        let window = self.htmlelement.element.node.owner_doc().document().window;
-        HTMLCollection::new(window, ~[])
+    pub fn Elements(&self) -> JS<HTMLCollection> {
+        let doc = self.htmlelement.element.node.owner_doc();
+        let doc = doc.get();
+        HTMLCollection::new(&doc.window, ~[])
     }
 
     pub fn WillValidate(&self) -> bool {
         false
     }
 
-    pub fn Validity(&self) -> @mut ValidityState {
-        let global = self.htmlelement.element.node.owner_doc().document().window;
-        ValidityState::new(global)
+    pub fn Validity(&self) -> JS<ValidityState> {
+        let doc = self.htmlelement.element.node.owner_doc();
+        let doc = doc.get();
+        ValidityState::new(&doc.window)
     }
 
     pub fn ValidationMessage(&self) -> DOMString {
diff --git a/src/components/script/dom/htmlfontelement.rs b/src/components/script/dom/htmlfontelement.rs
index b3ccf1a6f14..024d546cc41 100644
--- a/src/components/script/dom/htmlfontelement.rs
+++ b/src/components/script/dom/htmlfontelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLFontElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLFontElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLFontElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLFontElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLFontElementDerived for EventTarget {
+    fn is_htmlfontelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLFontElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLFontElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLFontElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLFontElement {
         HTMLFontElement {
             htmlelement: HTMLElement::new_inherited(HTMLFontElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLFontElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLFontElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLFontElement> {
+        let element = HTMLFontElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLFontElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlformelement.rs b/src/components/script/dom/htmlformelement.rs
index 554cabd6090..d213c68dbdb 100644
--- a/src/components/script/dom/htmlformelement.rs
+++ b/src/components/script/dom/htmlformelement.rs
@@ -3,28 +3,41 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLFormElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLFormElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
-use dom::element::HTMLFormElementTypeId;
+use dom::document::Document;
+use dom::element::{Element, HTMLFormElementTypeId};
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlcollection::HTMLCollection;
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLFormElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLFormElementDerived for EventTarget {
+    fn is_htmlformelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLFormElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLFormElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLFormElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLFormElement {
         HTMLFormElement {
             htmlelement: HTMLElement::new_inherited(HTMLFormElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLFormElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLFormElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLFormElement> {
+        let element = HTMLFormElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLFormElementBinding::Wrap)
     }
 }
 
@@ -101,9 +114,10 @@ impl HTMLFormElement {
         Ok(())
     }
 
-    pub fn Elements(&self) -> @mut HTMLCollection {
-        let window = self.htmlelement.element.node.owner_doc().document().window;
-        HTMLCollection::new(window, ~[])
+    pub fn Elements(&self) -> JS<HTMLCollection> {
+        let doc = self.htmlelement.element.node.owner_doc();
+        let doc = doc.get();
+        HTMLCollection::new(&doc.window, ~[])
     }
 
     pub fn Length(&self) -> i32 {
@@ -121,7 +135,7 @@ impl HTMLFormElement {
         false
     }
 
-    pub fn IndexedGetter(&self, _index: u32, _found: &mut bool) -> AbstractNode {
+    pub fn IndexedGetter(&self, _index: u32, _found: &mut bool) -> JS<Element> {
         fail!("Not implemented.")
     }
 }
diff --git a/src/components/script/dom/htmlframeelement.rs b/src/components/script/dom/htmlframeelement.rs
index 25e6feae0b6..26486c7cceb 100644
--- a/src/components/script/dom/htmlframeelement.rs
+++ b/src/components/script/dom/htmlframeelement.rs
@@ -3,28 +3,41 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLFrameElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLFrameElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLFrameElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use dom::windowproxy::WindowProxy;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLFrameElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLFrameElementDerived for EventTarget {
+    fn is_htmlframeelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLFrameElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLFrameElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLFrameElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLFrameElement {
         HTMLFrameElement {
             htmlelement: HTMLElement::new_inherited(HTMLFrameElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLFrameElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLFrameElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLFrameElement> {
+        let element = HTMLFrameElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLFrameElementBinding::Wrap)
     }
 }
 
@@ -77,11 +90,11 @@ impl HTMLFrameElement {
         Ok(())
     }
 
-    pub fn GetContentDocument(&self) -> Option<AbstractDocument> {
+    pub fn GetContentDocument(&self) -> Option<JS<Document>> {
         None
     }
 
-    pub fn GetContentWindow(&self) -> Option<@mut WindowProxy> {
+    pub fn GetContentWindow(&self) -> Option<JS<WindowProxy>> {
         None
     }
 
diff --git a/src/components/script/dom/htmlframesetelement.rs b/src/components/script/dom/htmlframesetelement.rs
index 5b40a4b5fe1..252c17709c5 100644
--- a/src/components/script/dom/htmlframesetelement.rs
+++ b/src/components/script/dom/htmlframesetelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLFrameSetElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLFrameSetElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLFrameSetElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLFrameSetElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLFrameSetElementDerived for EventTarget {
+    fn is_htmlframesetelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLFrameSetElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLFrameSetElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLFrameSetElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLFrameSetElement {
         HTMLFrameSetElement {
             htmlelement: HTMLElement::new_inherited(HTMLFrameSetElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLFrameSetElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLFrameSetElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLFrameSetElement> {
+        let element = HTMLFrameSetElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLFrameSetElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlheadelement.rs b/src/components/script/dom/htmlheadelement.rs
index f7459d0ac4f..91266180c27 100644
--- a/src/components/script/dom/htmlheadelement.rs
+++ b/src/components/script/dom/htmlheadelement.rs
@@ -3,25 +3,38 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLHeadElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLHeadElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLHeadElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLHeadElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLHeadElementDerived for EventTarget {
+    fn is_htmlheadelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLHeadElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLHeadElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLHeadElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLHeadElement {
         HTMLHeadElement {
             htmlelement: HTMLElement::new_inherited(HTMLHeadElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLHeadElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLHeadElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLHeadElement> {
+        let element = HTMLHeadElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLHeadElementBinding::Wrap)
     }
 }
diff --git a/src/components/script/dom/htmlheadingelement.rs b/src/components/script/dom/htmlheadingelement.rs
index f15075f30cd..ecae9910b6d 100644
--- a/src/components/script/dom/htmlheadingelement.rs
+++ b/src/components/script/dom/htmlheadingelement.rs
@@ -3,12 +3,16 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLHeadingElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLHeadingElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLHeadingElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub enum HeadingLevel {
     Heading1,
     Heading2,
@@ -18,22 +22,32 @@ pub enum HeadingLevel {
     Heading6,
 }
 
+#[deriving(Encodable)]
 pub struct HTMLHeadingElement {
     htmlelement: HTMLElement,
     level: HeadingLevel,
 }
 
+impl HTMLHeadingElementDerived for EventTarget {
+    fn is_htmlheadingelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLHeadingElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLHeadingElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument, level: HeadingLevel) -> HTMLHeadingElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>, level: HeadingLevel) -> HTMLHeadingElement {
         HTMLHeadingElement {
             htmlelement: HTMLElement::new_inherited(HTMLHeadingElementTypeId, localName, document),
             level: level,
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument, level: HeadingLevel) -> AbstractNode {
-        let element = HTMLHeadingElement::new_inherited(localName, document, level);
-        Node::reflect_node(@mut element, document, HTMLHeadingElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>, level: HeadingLevel) -> JS<HTMLHeadingElement> {
+        let element = HTMLHeadingElement::new_inherited(localName, document.clone(), level);
+        Node::reflect_node(~element, document, HTMLHeadingElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlhrelement.rs b/src/components/script/dom/htmlhrelement.rs
index 1a239a30049..557a423787c 100644
--- a/src/components/script/dom/htmlhrelement.rs
+++ b/src/components/script/dom/htmlhrelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLHRElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLHRElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLHRElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLHRElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLHRElementDerived for EventTarget {
+    fn is_htmlhrelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLHRElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLHRElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLHRElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLHRElement {
         HTMLHRElement {
             htmlelement: HTMLElement::new_inherited(HTMLHRElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLHRElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLHRElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLHRElement> {
+        let element = HTMLHRElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLHRElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlhtmlelement.rs b/src/components/script/dom/htmlhtmlelement.rs
index 2da7b45f40b..dcadd267abb 100644
--- a/src/components/script/dom/htmlhtmlelement.rs
+++ b/src/components/script/dom/htmlhtmlelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLHtmlElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLHtmlElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLHtmlElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLHtmlElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLHtmlElementDerived for EventTarget {
+    fn is_htmlhtmlelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLHtmlElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLHtmlElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLHtmlElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLHtmlElement {
         HTMLHtmlElement {
             htmlelement: HTMLElement::new_inherited(HTMLHtmlElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLHtmlElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLHtmlElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLHtmlElement> {
+        let element = HTMLHtmlElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLHtmlElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmliframeelement.rs b/src/components/script/dom/htmliframeelement.rs
index ca38c069d14..92e0c63dfc7 100644
--- a/src/components/script/dom/htmliframeelement.rs
+++ b/src/components/script/dom/htmliframeelement.rs
@@ -3,17 +3,21 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLIFrameElementBinding;
+use dom::bindings::codegen::InheritTypes::{ElementCast, HTMLIFrameElementDerived};
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLIframeElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use dom::windowproxy::WindowProxy;
 use servo_util::str::DOMString;
 
 use extra::url::Url;
 use servo_msg::constellation_msg::{PipelineId, SubpageId};
 use std::ascii::StrAsciiExt;
+use extra::serialize::{Encoder, Encodable};
 
 enum SandboxAllowance {
     AllowNothing = 0x00,
@@ -25,13 +29,33 @@ enum SandboxAllowance {
     AllowPopups = 0x20
 }
 
+#[deriving(Encodable)]
 pub struct HTMLIFrameElement {
     htmlelement: HTMLElement,
-    frame: Option<Url>,
+    extra: Untraceable,
     size: Option<IFrameSize>,
     sandbox: Option<u8>
 }
 
+struct Untraceable {
+    frame: Option<Url>,
+}
+
+impl<S: Encoder> Encodable<S> for Untraceable {
+    fn encode(&self, _s: &mut S) {
+    }
+}
+
+impl HTMLIFrameElementDerived for EventTarget {
+    fn is_htmliframeelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLIframeElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
+#[deriving(Encodable)]
 pub struct IFrameSize {
     pipeline_id: PipelineId,
     subpage_id: SubpageId,
@@ -44,18 +68,20 @@ impl HTMLIFrameElement {
 }
 
 impl HTMLIFrameElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLIFrameElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLIFrameElement {
         HTMLIFrameElement {
             htmlelement: HTMLElement::new_inherited(HTMLIframeElementTypeId, localName, document),
-            frame: None,
+            extra: Untraceable {
+                frame: None
+            },
             size: None,
             sandbox: None,
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLIFrameElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLIFrameElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLIFrameElement> {
+        let element = HTMLIFrameElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLIFrameElementBinding::Wrap)
     }
 }
 
@@ -84,12 +110,13 @@ impl HTMLIFrameElement {
         Ok(())
     }
 
-    pub fn Sandbox(&self, _abstract_self: AbstractNode) -> DOMString {
+    pub fn Sandbox(&self, _abstract_self: &JS<HTMLIFrameElement>) -> DOMString {
         self.htmlelement.element.get_string_attribute("sandbox")
     }
 
-    pub fn SetSandbox(&mut self, abstract_self: AbstractNode, sandbox: DOMString) {
-        self.htmlelement.element.set_string_attribute(abstract_self, "sandbox",
+    pub fn SetSandbox(&mut self, abstract_self: &JS<HTMLIFrameElement>, sandbox: DOMString) {
+        self.htmlelement.element.set_string_attribute(&ElementCast::from(abstract_self),
+                                                      "sandbox",
                                                       sandbox);
     }
 
@@ -143,11 +170,11 @@ impl HTMLIFrameElement {
         Ok(())
     }
 
-    pub fn GetContentDocument(&self) -> Option<AbstractDocument> {
+    pub fn GetContentDocument(&self) -> Option<JS<Document>> {
         None
     }
 
-    pub fn GetContentWindow(&self) -> Option<@mut WindowProxy> {
+    pub fn GetContentWindow(&self) -> Option<JS<WindowProxy>> {
         None
     }
 
@@ -199,7 +226,7 @@ impl HTMLIFrameElement {
         Ok(())
     }
 
-    pub fn GetSVGDocument(&self) -> Option<AbstractDocument> {
+    pub fn GetSVGDocument(&self) -> Option<JS<Document>> {
         None
     }
 }
diff --git a/src/components/script/dom/htmlimageelement.rs b/src/components/script/dom/htmlimageelement.rs
index 5e041572537..d2304944eeb 100644
--- a/src/components/script/dom/htmlimageelement.rs
+++ b/src/components/script/dom/htmlimageelement.rs
@@ -3,11 +3,15 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLImageElementBinding;
+use dom::bindings::codegen::InheritTypes::{NodeCast, HTMLImageElementDerived};
+use dom::bindings::codegen::InheritTypes::{ElementCast};
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
-use dom::element::HTMLImageElementTypeId;
+use dom::document::Document;
+use dom::element::{Element, HTMLImageElementTypeId};
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId, NodeHelpers};
 use extra::url::Url;
 use servo_util::geometry::to_px;
 use layout_interface::{ContentBoxQuery, ContentBoxResponse};
@@ -17,22 +21,45 @@ use servo_util::url::parse_url;
 use servo_util::namespace::Null;
 use servo_util::str::DOMString;
 
+use extra::serialize::{Encoder, Encodable};
+
+#[deriving(Encodable)]
 pub struct HTMLImageElement {
     htmlelement: HTMLElement,
+    extra: Untraceable,
+}
+
+struct Untraceable {
     image: Option<Url>,
 }
 
+impl<S: Encoder> Encodable<S> for Untraceable {
+    fn encode(&self, _s: &mut S) {
+    }
+}
+
+impl HTMLImageElementDerived for EventTarget {
+    fn is_htmlimageelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLImageElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLImageElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLImageElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLImageElement {
         HTMLImageElement {
             htmlelement: HTMLElement::new_inherited(HTMLImageElementTypeId, localName, document),
-            image: None,
+            extra: Untraceable {
+                image: None,
+            }
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLImageElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLImageElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLImageElement> {
+        let element = HTMLImageElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLImageElementBinding::Wrap)
     }
 }
 
@@ -41,12 +68,12 @@ impl HTMLImageElement {
     /// prefetching the image. This method must be called after `src` is changed.
     pub fn update_image(&mut self, image_cache: ImageCacheTask, url: Option<Url>) {
         let elem = &mut self.htmlelement.element;
-        let src_opt = elem.get_attribute(Null, "src").map(|x| x.Value());
+        let src_opt = elem.get_attribute(Null, "src").map(|x| x.get().Value());
         match src_opt {
             None => {}
             Some(src) => {
                 let img_url = parse_url(src, url);
-                self.image = Some(img_url.clone());
+                self.extra.image = Some(img_url.clone());
 
                 // inform the image cache to load this, but don't store a
                 // handle.
@@ -61,7 +88,7 @@ impl HTMLImageElement {
     pub fn AfterSetAttr(&mut self, name: DOMString, _value: DOMString) {
         if "src" == name {
             let document = self.htmlelement.element.node.owner_doc();
-            let window = document.document().window;
+            let window = document.get().window.get();
             let url = window.page.url.as_ref().map(|&(ref url, _)| url.clone());
             self.update_image(window.image_cache_task.clone(), url);
         }
@@ -73,7 +100,7 @@ impl HTMLImageElement {
         // `self.update_image()` will see the missing src attribute and return early.
         if "src" == name {
             let document = self.htmlelement.element.node.owner_doc();
-            let window = document.document().window;
+            let window = document.get().window.get();
             self.update_image(window.image_cache_task.clone(), None);
         }
     }
@@ -86,13 +113,13 @@ impl HTMLImageElement {
         Ok(())
     }
 
-    pub fn Src(&self, _abstract_self: AbstractNode) -> DOMString {
+    pub fn Src(&self, _abstract_self: &JS<HTMLImageElement>) -> DOMString {
         ~""
     }
 
-    pub fn SetSrc(&mut self, abstract_self: AbstractNode, src: DOMString) -> ErrorResult {
+    pub fn SetSrc(&mut self, abstract_self: &JS<HTMLImageElement>, src: DOMString) -> ErrorResult {
         let node = &mut self.htmlelement.element;
-        node.set_attr(abstract_self, ~"src", src.clone());
+        node.set_attr(&ElementCast::from(abstract_self), ~"src", src.clone());
         Ok(())
     }
 
@@ -120,37 +147,43 @@ impl HTMLImageElement {
         Ok(())
     }
 
-    pub fn Width(&self, abstract_self: AbstractNode) -> u32 {
-        let node = &self.htmlelement.element.node;
-        let page = node.owner_doc().document().window.page;
+    pub fn Width(&self, abstract_self: &JS<HTMLImageElement>) -> u32 {
+        let node: JS<Node> = NodeCast::from(abstract_self);
+        let doc = node.get().owner_doc();
+        let page = doc.get().window.get().page;
         let (port, chan) = Chan::new();
-        match page.query_layout(ContentBoxQuery(abstract_self, chan), port) {
+        let addr = node.to_trusted_node_address();
+        match page.query_layout(ContentBoxQuery(addr, chan), port) {
             ContentBoxResponse(rect) => {
                 to_px(rect.size.width) as u32
             }
         }
     }
 
-    pub fn SetWidth(&mut self, abstract_self: AbstractNode, width: u32) -> ErrorResult {
-        let node = &mut self.htmlelement.element;
-        node.set_attr(abstract_self, ~"width", width.to_str());
+    pub fn SetWidth(&mut self, abstract_self: &JS<HTMLImageElement>, width: u32) -> ErrorResult {
+        let mut elem: JS<Element> = ElementCast::from(abstract_self);
+        let mut elem_clone = elem.clone();
+        elem.get_mut().set_attr(&mut elem_clone, ~"width", width.to_str());
         Ok(())
     }
 
-    pub fn Height(&self, abstract_self: AbstractNode) -> u32 {
+    pub fn Height(&self, abstract_self: &JS<HTMLImageElement>) -> u32 {
         let node = &self.htmlelement.element.node;
-        let page = node.owner_doc().document().window.page;
+        let doc = node.owner_doc();
+        let page = doc.get().window.get().page;
         let (port, chan) = Chan::new();
-        match page.query_layout(ContentBoxQuery(abstract_self, chan), port) {
+        let this_node: JS<Node> = NodeCast::from(abstract_self);
+        let addr = this_node.to_trusted_node_address();
+        match page.query_layout(ContentBoxQuery(addr, chan), port) {
             ContentBoxResponse(rect) => {
                 to_px(rect.size.height) as u32
             }
         }
     }
 
-    pub fn SetHeight(&mut self, abstract_self: AbstractNode, height: u32) -> ErrorResult {
+    pub fn SetHeight(&mut self, abstract_self: &JS<HTMLImageElement>, height: u32) -> ErrorResult {
         let node = &mut self.htmlelement.element;
-        node.set_attr(abstract_self, ~"height", height.to_str());
+        node.set_attr(&ElementCast::from(abstract_self), ~"height", height.to_str());
         Ok(())
     }
 
diff --git a/src/components/script/dom/htmlinputelement.rs b/src/components/script/dom/htmlinputelement.rs
index d2f2acd0249..426f78b3e6b 100644
--- a/src/components/script/dom/htmlinputelement.rs
+++ b/src/components/script/dom/htmlinputelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLInputElementBinding;
-use dom::bindings::utils::{Fallible, ErrorResult};
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLInputElementDerived;
+use dom::bindings::js::JS;
+use dom::bindings::utils::{ErrorResult, Fallible};
+use dom::document::Document;
 use dom::element::HTMLInputElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLInputElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLInputElementDerived for EventTarget {
+    fn is_htmlinputelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLInputElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLInputElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLInputElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLInputElement {
         HTMLInputElement {
             htmlelement: HTMLElement::new_inherited(HTMLInputElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLInputElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLInputElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLInputElement> {
+        let element = HTMLInputElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLInputElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmllabelelement.rs b/src/components/script/dom/htmllabelelement.rs
index 89cf6215ca9..e4da3eb661c 100644
--- a/src/components/script/dom/htmllabelelement.rs
+++ b/src/components/script/dom/htmllabelelement.rs
@@ -3,26 +3,39 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLLabelElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLLabelElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLLabelElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLLabelElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLLabelElementDerived for EventTarget {
+    fn is_htmllabelelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLLabelElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLLabelElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLLabelElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLLabelElement {
         HTMLLabelElement {
             htmlelement: HTMLElement::new_inherited(HTMLLabelElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLLabelElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLLabelElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLLabelElement> {
+        let element = HTMLLabelElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLLabelElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmllegendelement.rs b/src/components/script/dom/htmllegendelement.rs
index 43949db6e82..9c98a6b103a 100644
--- a/src/components/script/dom/htmllegendelement.rs
+++ b/src/components/script/dom/htmllegendelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLLegendElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLLegendElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLLegendElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLLegendElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLLegendElementDerived for EventTarget {
+    fn is_htmllegendelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLLegendElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLLegendElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLLegendElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLLegendElement {
         HTMLLegendElement {
             htmlelement: HTMLElement::new_inherited(HTMLLegendElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLLegendElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLLegendElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLLegendElement> {
+        let element = HTMLLegendElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLLegendElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmllielement.rs b/src/components/script/dom/htmllielement.rs
index 2079df20568..79a243c7fb2 100644
--- a/src/components/script/dom/htmllielement.rs
+++ b/src/components/script/dom/htmllielement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLLIElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLLIElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLLIElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLLIElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLLIElementDerived for EventTarget {
+    fn is_htmllielement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLLIElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLLIElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLLIElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLLIElement {
         HTMLLIElement {
             htmlelement: HTMLElement::new_inherited(HTMLLIElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLLIElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLLIElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLLIElement> {
+        let element = HTMLLIElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLLIElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmllinkelement.rs b/src/components/script/dom/htmllinkelement.rs
index d5fce888632..f8e6bdc73e7 100644
--- a/src/components/script/dom/htmllinkelement.rs
+++ b/src/components/script/dom/htmllinkelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLLinkElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLLinkElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLLinkElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLLinkElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLLinkElementDerived for EventTarget {
+    fn is_htmllinkelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLLinkElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLLinkElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLLinkElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLLinkElement {
         HTMLLinkElement {
             htmlelement: HTMLElement::new_inherited(HTMLLinkElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLLinkElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLLinkElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLLinkElement> {
+        let element = HTMLLinkElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLLinkElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlmainelement.rs b/src/components/script/dom/htmlmainelement.rs
index 550e0470efb..b0fc11c2781 100644
--- a/src/components/script/dom/htmlmainelement.rs
+++ b/src/components/script/dom/htmlmainelement.rs
@@ -3,25 +3,38 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLMainElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLMainElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLMainElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLMainElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLMainElementDerived for EventTarget {
+    fn is_htmlmainelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLMainElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLMainElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLMainElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLMainElement {
         HTMLMainElement {
             htmlelement: HTMLElement::new_inherited(HTMLMainElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLMainElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLMainElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLMainElement> {
+        let element = HTMLMainElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLMainElementBinding::Wrap)
     }
 }
diff --git a/src/components/script/dom/htmlmapelement.rs b/src/components/script/dom/htmlmapelement.rs
index d61278ce070..fcb09820fb1 100644
--- a/src/components/script/dom/htmlmapelement.rs
+++ b/src/components/script/dom/htmlmapelement.rs
@@ -3,28 +3,41 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLMapElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLMapElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::htmlcollection::HTMLCollection;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLMapElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::htmlcollection::HTMLCollection;
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLMapElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLMapElementDerived for EventTarget {
+    fn is_htmlmapelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLMapElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLMapElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLMapElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLMapElement {
         HTMLMapElement {
             htmlelement: HTMLElement::new_inherited(HTMLMapElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLMapElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLMapElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLMapElement> {
+        let element = HTMLMapElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLMapElementBinding::Wrap)
     }
 }
 
@@ -37,8 +50,9 @@ impl HTMLMapElement {
         Ok(())
     }
 
-    pub fn Areas(&self) -> @mut HTMLCollection {
-        let window = self.htmlelement.element.node.owner_doc().document().window;
-        HTMLCollection::new(window, ~[])
+    pub fn Areas(&self) -> JS<HTMLCollection> {
+        let doc = self.htmlelement.element.node.owner_doc();
+        let doc = doc.get();
+        HTMLCollection::new(&doc.window, ~[])
     }
 }
diff --git a/src/components/script/dom/htmlmediaelement.rs b/src/components/script/dom/htmlmediaelement.rs
index 371374c4859..d28b38085de 100644
--- a/src/components/script/dom/htmlmediaelement.rs
+++ b/src/components/script/dom/htmlmediaelement.rs
@@ -2,18 +2,33 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::js::JS;
+use dom::bindings::codegen::InheritTypes::HTMLMediaElementDerived;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
-use dom::element::ElementTypeId;
+use dom::document::Document;
+use dom::element::{ElementTypeId, HTMLAudioElementTypeId, HTMLVideoElementTypeId};
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
+use dom::node::ElementNodeTypeId;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLMediaElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLMediaElementDerived for EventTarget {
+    fn is_htmlmediaelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLVideoElementTypeId)) |
+            NodeTargetTypeId(ElementNodeTypeId(HTMLAudioElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLMediaElement {
-    pub fn new_inherited(type_id: ElementTypeId, tag_name: DOMString, document: AbstractDocument) -> HTMLMediaElement {
+    pub fn new_inherited(type_id: ElementTypeId, tag_name: DOMString, document: JS<Document>) -> HTMLMediaElement {
         HTMLMediaElement {
             htmlelement: HTMLElement::new_inherited(type_id, tag_name, document)
         }
diff --git a/src/components/script/dom/htmlmetaelement.rs b/src/components/script/dom/htmlmetaelement.rs
index 254fe4c94f4..94639c05d0e 100644
--- a/src/components/script/dom/htmlmetaelement.rs
+++ b/src/components/script/dom/htmlmetaelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLMetaElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLMetaElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLMetaElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLMetaElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLMetaElementDerived for EventTarget {
+    fn is_htmlmetaelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLMetaElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLMetaElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLMetaElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLMetaElement {
         HTMLMetaElement {
             htmlelement: HTMLElement::new_inherited(HTMLMetaElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLMetaElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLMetaElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLMetaElement> {
+        let element = HTMLMetaElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLMetaElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlmeterelement.rs b/src/components/script/dom/htmlmeterelement.rs
index 3e179fa1743..ac7e4e04736 100644
--- a/src/components/script/dom/htmlmeterelement.rs
+++ b/src/components/script/dom/htmlmeterelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLMeterElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLMeterElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLMeterElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLMeterElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLMeterElementDerived for EventTarget {
+    fn is_htmlmeterelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLMeterElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLMeterElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLMeterElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLMeterElement {
         HTMLMeterElement {
             htmlelement: HTMLElement::new_inherited(HTMLMeterElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLMeterElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLMeterElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLMeterElement> {
+        let element = HTMLMeterElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLMeterElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlmodelement.rs b/src/components/script/dom/htmlmodelement.rs
index eb765ed0120..bd1b00f30f4 100644
--- a/src/components/script/dom/htmlmodelement.rs
+++ b/src/components/script/dom/htmlmodelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLModElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLModElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLModElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLModElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLModElementDerived for EventTarget {
+    fn is_htmlmodelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLModElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLModElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLModElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLModElement {
         HTMLModElement {
             htmlelement: HTMLElement::new_inherited(HTMLModElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLModElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLModElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLModElement> {
+        let element = HTMLModElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLModElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlobjectelement.rs b/src/components/script/dom/htmlobjectelement.rs
index 74f40db40dd..d373a0e6df4 100644
--- a/src/components/script/dom/htmlobjectelement.rs
+++ b/src/components/script/dom/htmlobjectelement.rs
@@ -3,11 +3,15 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLObjectElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLObjectElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLObjectElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::htmlformelement::HTMLFormElement;
+use dom::node::{Node, ElementNodeTypeId};
 use dom::validitystate::ValidityState;
 use dom::windowproxy::WindowProxy;
 use servo_util::str::DOMString;
@@ -19,20 +23,30 @@ use servo_util::url::parse_url;
 use servo_util::namespace::Null;
 use servo_util::url::is_image_data;
 
+#[deriving(Encodable)]
 pub struct HTMLObjectElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLObjectElementDerived for EventTarget {
+    fn is_htmlobjectelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLObjectElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLObjectElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLObjectElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLObjectElement {
         HTMLObjectElement {
             htmlelement: HTMLElement::new_inherited(HTMLObjectElementTypeId, localName, document),
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLObjectElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLObjectElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLObjectElement> {
+        let element = HTMLObjectElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLObjectElementBinding::Wrap)
     }
 }
 
@@ -44,8 +58,8 @@ impl HTMLObjectElement {
         let elem = &mut self.htmlelement.element;
 
         // TODO: support other values
-        match (elem.get_attribute(Null, "type").map(|x| x.Value()),
-               elem.get_attribute(Null, "data").map(|x| x.Value())) {
+        match (elem.get_attribute(Null, "type").map(|x| x.get().Value()),
+               elem.get_attribute(Null, "data").map(|x| x.get().Value())) {
             (None, Some(uri)) => {
                 if is_image_data(uri) {
                     let data_url = parse_url(uri, url);
@@ -60,9 +74,9 @@ impl HTMLObjectElement {
     pub fn AfterSetAttr(&mut self, name: DOMString, _value: DOMString) {
         if "data" == name {
             let document = self.htmlelement.element.node.owner_doc();
-            let window = document.document().window;
-            let url = window.page.url.as_ref().map(|&(ref url, _)| url.clone());
-            self.process_data_url(window.image_cache_task.clone(), url);
+            let window = document.get().window.clone();
+            let url = window.get().page.url.as_ref().map(|&(ref url, _)| url.clone());
+            self.process_data_url(window.get().image_cache_task.clone(), url);
         }
     }
 
@@ -98,7 +112,7 @@ impl HTMLObjectElement {
         Ok(())
     }
 
-    pub fn GetForm(&self) -> Option<AbstractNode> {
+    pub fn GetForm(&self) -> Option<JS<HTMLFormElement>> {
         None
     }
 
@@ -118,11 +132,11 @@ impl HTMLObjectElement {
         Ok(())
     }
 
-    pub fn GetContentDocument(&self) -> Option<AbstractDocument> {
+    pub fn GetContentDocument(&self) -> Option<JS<Document>> {
         None
     }
 
-    pub fn GetContentWindow(&self) -> Option<@mut WindowProxy> {
+    pub fn GetContentWindow(&self) -> Option<JS<WindowProxy>> {
         None
     }
 
@@ -130,9 +144,10 @@ impl HTMLObjectElement {
         false
     }
 
-    pub fn Validity(&self) -> @mut ValidityState {
-        let global = self.htmlelement.element.node.owner_doc().document().window;
-        ValidityState::new(global)
+    pub fn Validity(&self) -> JS<ValidityState> {
+        let doc = self.htmlelement.element.node.owner_doc();
+        let doc = doc.get();
+        ValidityState::new(&doc.window)
     }
 
     pub fn ValidationMessage(&self) -> DOMString {
@@ -226,7 +241,7 @@ impl HTMLObjectElement {
         Ok(())
     }
 
-    pub fn GetSVGDocument(&self) -> Option<AbstractDocument> {
+    pub fn GetSVGDocument(&self) -> Option<JS<Document>> {
         None
     }
 }
diff --git a/src/components/script/dom/htmlolistelement.rs b/src/components/script/dom/htmlolistelement.rs
index 6a762b31147..ea677919edb 100644
--- a/src/components/script/dom/htmlolistelement.rs
+++ b/src/components/script/dom/htmlolistelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLOListElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLOListElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLOListElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLOListElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLOListElementDerived for EventTarget {
+    fn is_htmlolistelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLOListElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLOListElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLOListElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLOListElement {
         HTMLOListElement {
             htmlelement: HTMLElement::new_inherited(HTMLOListElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLOListElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLOListElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLOListElement> {
+        let element = HTMLOListElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLOListElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmloptgroupelement.rs b/src/components/script/dom/htmloptgroupelement.rs
index 020dd3a2471..d8a3d222cb3 100644
--- a/src/components/script/dom/htmloptgroupelement.rs
+++ b/src/components/script/dom/htmloptgroupelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLOptGroupElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLOptGroupElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLOptGroupElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLOptGroupElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLOptGroupElementDerived for EventTarget {
+    fn is_htmloptgroupelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLOptGroupElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLOptGroupElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLOptGroupElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLOptGroupElement {
         HTMLOptGroupElement {
             htmlelement: HTMLElement::new_inherited(HTMLOptGroupElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLOptGroupElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLOptGroupElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLOptGroupElement> {
+        let element = HTMLOptGroupElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLOptGroupElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmloptionelement.rs b/src/components/script/dom/htmloptionelement.rs
index d1761ecdd1a..d01de54a8bc 100644
--- a/src/components/script/dom/htmloptionelement.rs
+++ b/src/components/script/dom/htmloptionelement.rs
@@ -3,27 +3,41 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLOptionElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLOptionElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLOptionElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::htmlformelement::HTMLFormElement;
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLOptionElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLOptionElementDerived for EventTarget {
+    fn is_htmloptionelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLOptionElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLOptionElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLOptionElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLOptionElement {
         HTMLOptionElement {
             htmlelement: HTMLElement::new_inherited(HTMLOptionElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLOptionElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLOptionElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLOptionElement> {
+        let element = HTMLOptionElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLOptionElementBinding::Wrap)
     }
 }
 
@@ -36,7 +50,7 @@ impl HTMLOptionElement {
         Ok(())
     }
 
-    pub fn GetForm(&self) -> Option<AbstractNode> {
+    pub fn GetForm(&self) -> Option<JS<HTMLFormElement>> {
         None
     }
 
diff --git a/src/components/script/dom/htmloutputelement.rs b/src/components/script/dom/htmloutputelement.rs
index 174e9258ecf..95c03763c3c 100644
--- a/src/components/script/dom/htmloutputelement.rs
+++ b/src/components/script/dom/htmloutputelement.rs
@@ -3,33 +3,47 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLOutputElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLOutputElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLOutputElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::htmlformelement::HTMLFormElement;
+use dom::node::{Node, ElementNodeTypeId};
 use dom::validitystate::ValidityState;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLOutputElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLOutputElementDerived for EventTarget {
+    fn is_htmloutputelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLOutputElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLOutputElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLOutputElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLOutputElement {
         HTMLOutputElement {
             htmlelement: HTMLElement::new_inherited(HTMLOutputElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLOutputElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLOutputElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLOutputElement> {
+        let element = HTMLOutputElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLOutputElementBinding::Wrap)
     }
 }
 
 impl HTMLOutputElement {
-    pub fn GetForm(&self) -> Option<AbstractNode> {
+    pub fn GetForm(&self) -> Option<JS<HTMLFormElement>> {
         None
     }
 
@@ -68,12 +82,13 @@ impl HTMLOutputElement {
     pub fn SetWillValidate(&mut self, _will_validate: bool) {
     }
 
-    pub fn Validity(&self) -> @mut ValidityState {
-        let global = self.htmlelement.element.node.owner_doc().document().window;
-        ValidityState::new(global)
+    pub fn Validity(&self) -> JS<ValidityState> {
+        let doc = self.htmlelement.element.node.owner_doc();
+        let doc = doc.get();
+        ValidityState::new(&doc.window)
     }
 
-    pub fn SetValidity(&mut self, _validity: @mut ValidityState) {
+    pub fn SetValidity(&mut self, _validity: JS<ValidityState>) {
     }
 
     pub fn ValidationMessage(&self) -> DOMString {
diff --git a/src/components/script/dom/htmlparagraphelement.rs b/src/components/script/dom/htmlparagraphelement.rs
index 1132a496f26..a1aef4a7f5d 100644
--- a/src/components/script/dom/htmlparagraphelement.rs
+++ b/src/components/script/dom/htmlparagraphelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLParagraphElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLParagraphElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLParagraphElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLParagraphElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLParagraphElementDerived for EventTarget {
+    fn is_htmlparagraphelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLParagraphElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLParagraphElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLParagraphElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLParagraphElement {
         HTMLParagraphElement {
             htmlelement: HTMLElement::new_inherited(HTMLParagraphElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLParagraphElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLParagraphElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLParagraphElement> {
+        let element = HTMLParagraphElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLParagraphElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlparamelement.rs b/src/components/script/dom/htmlparamelement.rs
index 3cd242e0016..1e3e7785c0d 100644
--- a/src/components/script/dom/htmlparamelement.rs
+++ b/src/components/script/dom/htmlparamelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLParamElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLParamElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLParamElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLParamElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLParamElementDerived for EventTarget {
+    fn is_htmlparamelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLParamElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLParamElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLParamElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLParamElement {
         HTMLParamElement {
             htmlelement: HTMLElement::new_inherited(HTMLParamElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLParamElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLParamElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLParamElement> {
+        let element = HTMLParamElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLParamElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlpreelement.rs b/src/components/script/dom/htmlpreelement.rs
index c2bf04464f3..33f5b1a7247 100644
--- a/src/components/script/dom/htmlpreelement.rs
+++ b/src/components/script/dom/htmlpreelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLPreElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLPreElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{ErrorResult};
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLPreElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLPreElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLPreElementDerived for EventTarget {
+    fn is_htmlpreelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLPreElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLPreElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLPreElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLPreElement {
         HTMLPreElement {
             htmlelement: HTMLElement::new_inherited(HTMLPreElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLPreElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLPreElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLPreElement> {
+        let element = HTMLPreElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLPreElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlprogresselement.rs b/src/components/script/dom/htmlprogresselement.rs
index dca693fa9d3..ee6b3bff48b 100644
--- a/src/components/script/dom/htmlprogresselement.rs
+++ b/src/components/script/dom/htmlprogresselement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLProgressElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLProgressElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{ErrorResult, Fallible};
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLProgressElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLProgressElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLProgressElementDerived for EventTarget {
+    fn is_htmlprogresselement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLProgressElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLProgressElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLProgressElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLProgressElement {
         HTMLProgressElement {
             htmlelement: HTMLElement::new_inherited(HTMLProgressElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLProgressElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLProgressElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLProgressElement> {
+        let element = HTMLProgressElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLProgressElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlquoteelement.rs b/src/components/script/dom/htmlquoteelement.rs
index 3ad246f16c2..9fc115dcf9c 100644
--- a/src/components/script/dom/htmlquoteelement.rs
+++ b/src/components/script/dom/htmlquoteelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLQuoteElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLQuoteElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLQuoteElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLQuoteElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLQuoteElementDerived for EventTarget {
+    fn is_htmlquoteelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLQuoteElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLQuoteElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLQuoteElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLQuoteElement {
         HTMLQuoteElement {
             htmlelement: HTMLElement::new_inherited(HTMLQuoteElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLQuoteElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLQuoteElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLQuoteElement> {
+        let element = HTMLQuoteElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLQuoteElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlscriptelement.rs b/src/components/script/dom/htmlscriptelement.rs
index 80513d5f649..191d588585b 100644
--- a/src/components/script/dom/htmlscriptelement.rs
+++ b/src/components/script/dom/htmlscriptelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLScriptElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLScriptElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLScriptElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLScriptElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLScriptElementDerived for EventTarget {
+    fn is_htmlscriptelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLScriptElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLScriptElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLScriptElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLScriptElement {
         HTMLScriptElement {
             htmlelement: HTMLElement::new_inherited(HTMLScriptElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLScriptElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLScriptElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLScriptElement> {
+        let element = HTMLScriptElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLScriptElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlselectelement.rs b/src/components/script/dom/htmlselectelement.rs
index 61fb132dfe2..1b7e452a992 100644
--- a/src/components/script/dom/htmlselectelement.rs
+++ b/src/components/script/dom/htmlselectelement.rs
@@ -3,28 +3,44 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLSelectElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLSelectElementDerived;
+use dom::bindings::codegen::UnionTypes::{HTMLElementOrLong, HTMLOptionElementOrHTMLOptGroupElement};
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
-use dom::element::HTMLSelectElementTypeId;
+use dom::document::Document;
+use dom::element::{Element, HTMLSelectElementTypeId};
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::htmlformelement::HTMLFormElement;
+use dom::node::{Node, ElementNodeTypeId};
+use dom::htmloptionelement::HTMLOptionElement;
 use dom::validitystate::ValidityState;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLSelectElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLSelectElementDerived for EventTarget {
+    fn is_htmlselectelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLSelectElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLSelectElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLSelectElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLSelectElement {
         HTMLSelectElement {
             htmlelement: HTMLElement::new_inherited(HTMLSelectElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLSelectElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLSelectElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLSelectElement> {
+        let element = HTMLSelectElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLSelectElementBinding::Wrap)
     }
 }
 
@@ -45,7 +61,7 @@ impl HTMLSelectElement {
         Ok(())
     }
 
-    pub fn GetForm(&self) -> Option<AbstractNode> {
+    pub fn GetForm(&self) -> Option<JS<HTMLFormElement>> {
         None
     }
 
@@ -93,19 +109,19 @@ impl HTMLSelectElement {
         Ok(())
     }
 
-    pub fn Item(&self, _index: u32) -> Option<AbstractNode> {
+    pub fn Item(&self, _index: u32) -> Option<JS<Element>> {
         None
     }
 
-    pub fn NamedItem(&self, _name: DOMString) -> Option<AbstractNode> {
+    pub fn NamedItem(&self, _name: DOMString) -> Option<JS<HTMLOptionElement>> {
         None
     }
 
-    pub fn IndexedGetter(&self, _index: u32, _found: &mut bool) -> Option<AbstractNode> {
+    pub fn IndexedGetter(&self, _index: u32, _found: &mut bool) -> Option<JS<Element>> {
         None
     }
 
-    pub fn IndexedSetter(&mut self, _index: u32, _option: Option<AbstractNode>) -> ErrorResult {
+    pub fn IndexedSetter(&mut self, _index: u32, _option: Option<JS<HTMLOptionElement>>) -> ErrorResult {
         Ok(())
     }
 
@@ -137,12 +153,13 @@ impl HTMLSelectElement {
     pub fn SetWillValidate(&mut self, _will_validate: bool) {
     }
 
-    pub fn Validity(&self) -> @mut ValidityState {
-        let global = self.htmlelement.element.node.owner_doc().document().window;
-        ValidityState::new(global)
+    pub fn Validity(&self) -> JS<ValidityState> {
+        let doc = self.htmlelement.element.node.owner_doc();
+        let doc = doc.get();
+        ValidityState::new(&doc.window)
     }
 
-    pub fn SetValidity(&mut self, _validity: @mut ValidityState) {
+    pub fn SetValidity(&mut self, _validity: JS<ValidityState>) {
     }
 
     pub fn ValidationMessage(&self) -> DOMString {
@@ -159,4 +176,8 @@ impl HTMLSelectElement {
 
     pub fn SetCustomValidity(&mut self, _error: DOMString) {
     }
+
+    pub fn Add(&self, _element: HTMLOptionElementOrHTMLOptGroupElement, _before: Option<HTMLElementOrLong>) -> ErrorResult {
+        Ok(())
+    }
 }
diff --git a/src/components/script/dom/htmlserializer.rs b/src/components/script/dom/htmlserializer.rs
index 97198b0ab79..482c724666b 100644
--- a/src/components/script/dom/htmlserializer.rs
+++ b/src/components/script/dom/htmlserializer.rs
@@ -4,10 +4,20 @@
 
 use servo_util::namespace;
 use dom::attr::Attr;
+use dom::bindings::codegen::InheritTypes::{ElementCast, TextCast, CommentCast};
+use dom::bindings::codegen::InheritTypes::{DocumentTypeCast, CharacterDataCast};
+use dom::bindings::codegen::InheritTypes::ProcessingInstructionCast;
+use dom::bindings::js::JS;
+use dom::characterdata::CharacterData;
+use dom::comment::Comment;
+use dom::documenttype::DocumentType;
+use dom::element::Element;
 use dom::node::NodeIterator;
 use dom::node::{DoctypeNodeTypeId, DocumentFragmentNodeTypeId, CommentNodeTypeId};
 use dom::node::{DocumentNodeTypeId, ElementNodeTypeId, ProcessingInstructionNodeTypeId};
-use dom::node::{TextNodeTypeId, AbstractNode};
+use dom::node::{TextNodeTypeId, NodeHelpers};
+use dom::processinginstruction::ProcessingInstruction;
+use dom::text::Text;
 
 pub fn serialize(iterator: &mut NodeIterator) -> ~str {
     let mut html = ~"";
@@ -20,28 +30,33 @@ pub fn serialize(iterator: &mut NodeIterator) -> ~str {
         html.push_str(
             match node.type_id() {
                 ElementNodeTypeId(..) => {
-                    serialize_elem(node, &mut open_elements)
+                    let elem: JS<Element> = ElementCast::to(&node);
+                    serialize_elem(&elem, &mut open_elements)
                 }
                 CommentNodeTypeId => {
-                    serialize_comment(node)
+                    let comment: JS<Comment> = CommentCast::to(&node);
+                    serialize_comment(&comment)
                 }
                 TextNodeTypeId => {
-                    serialize_text(node)
+                    let text: JS<Text> = TextCast::to(&node);
+                    serialize_text(&text)
                 }
                 DoctypeNodeTypeId => {
-                    serialize_doctype(node)
+                    let doctype: JS<DocumentType> = DocumentTypeCast::to(&node);
+                    serialize_doctype(&doctype)
                 }
                 ProcessingInstructionNodeTypeId => {
-                    serialize_processing_instruction(node)
+                    let processing_instruction: JS<ProcessingInstruction> = ProcessingInstructionCast::to(&node);
+                    serialize_processing_instruction(&processing_instruction)
                 }
                 DocumentFragmentNodeTypeId => {
                     ~""
                 }
-                DocumentNodeTypeId(_) => {
+                DocumentNodeTypeId => {
                     fail!("It shouldn't be possible to serialize a document node")
                 }
             }
-            );
+        );
     }
     while open_elements.len() > 0 {
         html.push_str(~"</" + open_elements.pop() + ">");
@@ -49,88 +64,75 @@ pub fn serialize(iterator: &mut NodeIterator) -> ~str {
     html
 }
 
-fn serialize_comment(node: AbstractNode) -> ~str {
-    node.with_imm_characterdata(|comment| {
-        ~"<!--" + comment.data + "-->"
-    })
+fn serialize_comment(comment: &JS<Comment>) -> ~str {
+    ~"<!--" + comment.get().characterdata.data + "-->"
 }
 
-fn serialize_text(node: AbstractNode) -> ~str {
-    node.with_imm_characterdata(|text| {
-        match node.parent_node() {
-            Some(parent) if parent.is_element() => {
-                parent.with_imm_element(|elem| {
-                    match elem.tag_name.as_slice() {
-                        "style" | "script" | "xmp" | "iframe" |
-                        "noembed" | "noframes" | "plaintext" |
-                        "noscript" if elem.namespace == namespace::HTML => {
-                            text.data.clone()
-                        },
-                        _ => escape(text.data, false)
-                    }
-               })
-            },
-            _ => escape(text.data, false)
+fn serialize_text(text: &JS<Text>) -> ~str {
+    match text.get().characterdata.node.parent_node {
+        Some(ref parent) if parent.is_element() => {
+            let elem: JS<Element> = ElementCast::to(parent);
+            match elem.get().tag_name.as_slice() {
+                "style" | "script" | "xmp" | "iframe" |
+                "noembed" | "noframes" | "plaintext" |
+                "noscript" if elem.get().namespace == namespace::HTML => {
+                    text.get().characterdata.data.clone()
+                },
+                _ => escape(text.get().characterdata.data, false)
+            }
         }
-    })
+        _ => escape(text.get().characterdata.data, false)
+    }
 }
 
-fn serialize_processing_instruction(node: AbstractNode) -> ~str {
-    node.with_imm_processing_instruction(|processing_instruction| {
-        ~"<?" + processing_instruction.target + " " + processing_instruction.characterdata.data + "?>"
-    })
+fn serialize_processing_instruction(processing_instruction: &JS<ProcessingInstruction>) -> ~str {
+    ~"<?" + processing_instruction.get().target + " " + processing_instruction.get().characterdata.data + "?>"
 }
 
-fn serialize_doctype(node: AbstractNode) -> ~str {
-    node.with_imm_doctype(|doctype| {
-        ~"<!DOCTYPE" + doctype.name + ">"
-    })
+fn serialize_doctype(doctype: &JS<DocumentType>) -> ~str {
+    ~"<!DOCTYPE" + doctype.get().name + ">"
 }
 
-fn serialize_elem(node: AbstractNode, open_elements: &mut ~[~str]) -> ~str {
-    node.with_imm_element(|elem| {
-        let mut rv = ~"<" + elem.tag_name;
-        for attr in elem.attrs.iter() {
-            rv.push_str(serialize_attr(attr));
-        };
-        rv.push_str(">");
-        match elem.tag_name.as_slice() {
-            "pre" | "listing" | "textarea" if
-                elem.namespace == namespace::HTML => {
-                    match node.first_child() {
-                        Some(child) if child.is_text() => {
-                            child.with_imm_characterdata(|text| {
-                                if text.data[0] == 0x0A as u8 {
-                                    rv.push_str("\x0A");
-                                }
-                            })
-                        },
-                        _ => {}
+fn serialize_elem(elem: &JS<Element>, open_elements: &mut ~[~str]) -> ~str {
+    let mut rv = ~"<" + elem.get().tag_name;
+    for attr in elem.get().attrs.iter() {
+        rv.push_str(serialize_attr(attr));
+    };
+    rv.push_str(">");
+    match elem.get().tag_name.as_slice() {
+        "pre" | "listing" | "textarea" if elem.get().namespace == namespace::HTML => {
+            match elem.get().node.first_child {
+                Some(ref child) if child.is_text() => {
+                    let text: JS<CharacterData> = CharacterDataCast::to(child);
+                    if text.get().data[0] == 0x0A as u8 {
+                        rv.push_str("\x0A");
                     }
-            },
-            _ => {}
-        }
-        if !elem.is_void() {
-            open_elements.push(elem.tag_name.clone());
-        }
-        rv
-    })
+                },
+                _ => {}
+            }
+        },
+        _ => {}
+    }
+    if !elem.get().is_void() {
+        open_elements.push(elem.get().tag_name.clone());
+    }
+    rv
 }
 
-fn serialize_attr(attr: &@mut Attr) -> ~str {
-    let attr_name = if attr.namespace == namespace::XML {
-        ~"xml:" + attr.local_name.clone()
-    } else if attr.namespace == namespace::XMLNS &&
-        attr.local_name.as_slice() == "xmlns" {
+fn serialize_attr(attr: &JS<Attr>) -> ~str {
+    let attr_name = if attr.get().namespace == namespace::XML {
+        ~"xml:" + attr.get().local_name.clone()
+    } else if attr.get().namespace == namespace::XMLNS &&
+        attr.get().local_name.as_slice() == "xmlns" {
         ~"xmlns"
-    } else if attr.namespace == namespace::XMLNS {
-        ~"xmlns:" + attr.local_name.clone()
-    } else if attr.namespace == namespace::XLink {
-        ~"xlink:" + attr.local_name.clone()
+    } else if attr.get().namespace == namespace::XMLNS {
+        ~"xmlns:" + attr.get().local_name.clone()
+    } else if attr.get().namespace == namespace::XLink {
+        ~"xlink:" + attr.get().local_name.clone()
     } else {
-        attr.name.clone()
+        attr.get().name.clone()
     };
-    ~" " + attr_name + "=\"" + escape(attr.value, true) + "\""
+    ~" " + attr_name + "=\"" + escape(attr.get().value, true) + "\""
 }
 
 fn escape(string: &str, attr_mode: bool) -> ~str {
diff --git a/src/components/script/dom/htmlsourceelement.rs b/src/components/script/dom/htmlsourceelement.rs
index 212ddd77850..c5c7beaec13 100644
--- a/src/components/script/dom/htmlsourceelement.rs
+++ b/src/components/script/dom/htmlsourceelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLSourceElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLSourceElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLSourceElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLSourceElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLSourceElementDerived for EventTarget {
+    fn is_htmlsourceelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLSourceElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLSourceElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLSourceElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLSourceElement {
         HTMLSourceElement {
             htmlelement: HTMLElement::new_inherited(HTMLSourceElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLSourceElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLSourceElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLSourceElement> {
+        let element = HTMLSourceElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLSourceElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlspanelement.rs b/src/components/script/dom/htmlspanelement.rs
index 47a47f3a17e..8b827bbf234 100644
--- a/src/components/script/dom/htmlspanelement.rs
+++ b/src/components/script/dom/htmlspanelement.rs
@@ -3,25 +3,38 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLSpanElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLSpanElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLSpanElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLSpanElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLSpanElementDerived for EventTarget {
+    fn is_htmlspanelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLSpanElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLSpanElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLSpanElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLSpanElement {
         HTMLSpanElement {
             htmlelement: HTMLElement::new_inherited(HTMLSpanElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLSpanElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLSpanElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLSpanElement> {
+        let element = HTMLSpanElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLSpanElementBinding::Wrap)
     }
 }
diff --git a/src/components/script/dom/htmlstyleelement.rs b/src/components/script/dom/htmlstyleelement.rs
index 4a39f6bcf39..bc12ca5a291 100644
--- a/src/components/script/dom/htmlstyleelement.rs
+++ b/src/components/script/dom/htmlstyleelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLStyleElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLStyleElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLStyleElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLStyleElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLStyleElementDerived for EventTarget {
+    fn is_htmlstyleelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLStyleElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLStyleElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLStyleElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLStyleElement {
         HTMLStyleElement {
             htmlelement: HTMLElement::new_inherited(HTMLStyleElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLStyleElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLStyleElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLStyleElement> {
+        let element = HTMLStyleElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLStyleElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmltablecaptionelement.rs b/src/components/script/dom/htmltablecaptionelement.rs
index 94d5faf5ffc..0599e2624bf 100644
--- a/src/components/script/dom/htmltablecaptionelement.rs
+++ b/src/components/script/dom/htmltablecaptionelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTableCaptionElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLTableCaptionElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLTableCaptionElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTableCaptionElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLTableCaptionElementDerived for EventTarget {
+    fn is_htmltablecaptionelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTableCaptionElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTableCaptionElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTableCaptionElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTableCaptionElement {
         HTMLTableCaptionElement {
             htmlelement: HTMLElement::new_inherited(HTMLTableCaptionElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTableCaptionElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTableCaptionElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTableCaptionElement> {
+        let element = HTMLTableCaptionElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTableCaptionElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmltablecellelement.rs b/src/components/script/dom/htmltablecellelement.rs
index ddca4692373..04c745affd4 100644
--- a/src/components/script/dom/htmltablecellelement.rs
+++ b/src/components/script/dom/htmltablecellelement.rs
@@ -2,18 +2,33 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::codegen::InheritTypes::HTMLTableCellElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
-use dom::element::ElementTypeId;
+use dom::document::Document;
+use dom::element::{ElementTypeId, HTMLTableDataCellElementTypeId, HTMLTableHeaderCellElementTypeId};
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
+use dom::node::ElementNodeTypeId;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTableCellElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLTableCellElementDerived for EventTarget {
+    fn is_htmltablecellelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTableDataCellElementTypeId)) |
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTableHeaderCellElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTableCellElement {
-    pub fn new_inherited(type_id: ElementTypeId, tag_name: DOMString, document: AbstractDocument) -> HTMLTableCellElement {
+    pub fn new_inherited(type_id: ElementTypeId, tag_name: DOMString, document: JS<Document>) -> HTMLTableCellElement {
         HTMLTableCellElement {
             htmlelement: HTMLElement::new_inherited(type_id, tag_name, document)
         }
diff --git a/src/components/script/dom/htmltablecolelement.rs b/src/components/script/dom/htmltablecolelement.rs
index 577718f5535..8fbdb208124 100644
--- a/src/components/script/dom/htmltablecolelement.rs
+++ b/src/components/script/dom/htmltablecolelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTableColElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLTableColElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLTableColElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTableColElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLTableColElementDerived for EventTarget {
+    fn is_htmltablecolelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTableColElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTableColElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTableColElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTableColElement {
         HTMLTableColElement {
             htmlelement: HTMLElement::new_inherited(HTMLTableColElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTableColElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTableColElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTableColElement> {
+        let element = HTMLTableColElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTableColElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmltabledatacellelement.rs b/src/components/script/dom/htmltabledatacellelement.rs
index edcfaae6053..f245f209513 100644
--- a/src/components/script/dom/htmltabledatacellelement.rs
+++ b/src/components/script/dom/htmltabledatacellelement.rs
@@ -3,25 +3,38 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTableDataCellElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLTableDataCellElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLTableDataCellElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmltablecellelement::HTMLTableCellElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTableDataCellElement {
     htmltablecellelement: HTMLTableCellElement,
 }
 
+impl HTMLTableDataCellElementDerived for EventTarget {
+    fn is_htmltabledatacellelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTableDataCellElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTableDataCellElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTableDataCellElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTableDataCellElement {
         HTMLTableDataCellElement {
             htmltablecellelement: HTMLTableCellElement::new_inherited(HTMLTableDataCellElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTableDataCellElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTableDataCellElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTableDataCellElement> {
+        let element = HTMLTableDataCellElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTableDataCellElementBinding::Wrap)
     }
 }
diff --git a/src/components/script/dom/htmltableelement.rs b/src/components/script/dom/htmltableelement.rs
index bf46faa3bcc..4ebd2cc4c97 100644
--- a/src/components/script/dom/htmltableelement.rs
+++ b/src/components/script/dom/htmltableelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTableElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLTableElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLTableElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTableElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLTableElementDerived for EventTarget {
+    fn is_htmltableelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTableElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTableElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTableElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTableElement {
         HTMLTableElement {
             htmlelement: HTMLElement::new_inherited(HTMLTableElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTableElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTableElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTableElement> {
+        let element = HTMLTableElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTableElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmltableheadercellelement.rs b/src/components/script/dom/htmltableheadercellelement.rs
index ed9475f3683..66b94da6b4c 100644
--- a/src/components/script/dom/htmltableheadercellelement.rs
+++ b/src/components/script/dom/htmltableheadercellelement.rs
@@ -3,25 +3,38 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTableHeaderCellElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLTableHeaderCellElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLTableHeaderCellElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmltablecellelement::HTMLTableCellElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTableHeaderCellElement {
     htmltablecellelement: HTMLTableCellElement,
 }
 
+impl HTMLTableHeaderCellElementDerived for EventTarget {
+    fn is_htmltableheadercellelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTableHeaderCellElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTableHeaderCellElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTableHeaderCellElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTableHeaderCellElement {
         HTMLTableHeaderCellElement {
             htmltablecellelement: HTMLTableCellElement::new_inherited(HTMLTableHeaderCellElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTableHeaderCellElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTableHeaderCellElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTableHeaderCellElement> {
+        let element = HTMLTableHeaderCellElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTableHeaderCellElementBinding::Wrap)
     }
 }
diff --git a/src/components/script/dom/htmltablerowelement.rs b/src/components/script/dom/htmltablerowelement.rs
index 53c5eaaa0b3..22ae9fa7071 100644
--- a/src/components/script/dom/htmltablerowelement.rs
+++ b/src/components/script/dom/htmltablerowelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTableRowElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLTableRowElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLTableRowElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTableRowElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLTableRowElementDerived for EventTarget {
+    fn is_htmltablerowelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTableRowElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTableRowElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTableRowElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTableRowElement {
         HTMLTableRowElement {
             htmlelement: HTMLElement::new_inherited(HTMLTableRowElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTableRowElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTableRowElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTableRowElement> {
+        let element = HTMLTableRowElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTableRowElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmltablesectionelement.rs b/src/components/script/dom/htmltablesectionelement.rs
index 7a3270197cb..f718e67586a 100644
--- a/src/components/script/dom/htmltablesectionelement.rs
+++ b/src/components/script/dom/htmltablesectionelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTableSectionElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLTableSectionElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLTableSectionElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTableSectionElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLTableSectionElementDerived for EventTarget {
+    fn is_htmltablesectionelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTableSectionElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTableSectionElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTableSectionElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTableSectionElement {
         HTMLTableSectionElement {
             htmlelement: HTMLElement::new_inherited(HTMLTableSectionElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTableSectionElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTableSectionElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTableSectionElement> {
+        let element = HTMLTableSectionElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTableSectionElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmltemplateelement.rs b/src/components/script/dom/htmltemplateelement.rs
index 1bfe4f0b236..ffb7cd7e771 100644
--- a/src/components/script/dom/htmltemplateelement.rs
+++ b/src/components/script/dom/htmltemplateelement.rs
@@ -3,25 +3,38 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTemplateElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLTemplateElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLTemplateElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTemplateElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLTemplateElementDerived for EventTarget {
+    fn is_htmltemplateelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTemplateElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTemplateElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTemplateElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTemplateElement {
         HTMLTemplateElement {
             htmlelement: HTMLElement::new_inherited(HTMLTemplateElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTemplateElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTemplateElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTemplateElement> {
+        let element = HTMLTemplateElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTemplateElementBinding::Wrap)
     }
 }
diff --git a/src/components/script/dom/htmltextareaelement.rs b/src/components/script/dom/htmltextareaelement.rs
index 43da53af73b..b34dc05c3e3 100644
--- a/src/components/script/dom/htmltextareaelement.rs
+++ b/src/components/script/dom/htmltextareaelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTextAreaElementBinding;
-use dom::bindings::utils::{Fallible, ErrorResult};
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLTextAreaElementDerived;
+use dom::bindings::js::JS;
+use dom::bindings::utils::{ErrorResult, Fallible};
+use dom::document::Document;
 use dom::element::HTMLTextAreaElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTextAreaElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLTextAreaElementDerived for EventTarget {
+    fn is_htmltextareaelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTextAreaElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTextAreaElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTextAreaElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTextAreaElement {
         HTMLTextAreaElement {
             htmlelement: HTMLElement::new_inherited(HTMLTextAreaElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTextAreaElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTextAreaElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTextAreaElement> {
+        let element = HTMLTextAreaElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTextAreaElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmltimeelement.rs b/src/components/script/dom/htmltimeelement.rs
index 23c48c71f70..baddd3bd908 100644
--- a/src/components/script/dom/htmltimeelement.rs
+++ b/src/components/script/dom/htmltimeelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTimeElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLTimeElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLTimeElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTimeElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLTimeElementDerived for EventTarget {
+    fn is_htmltimeelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTimeElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTimeElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTimeElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTimeElement {
         HTMLTimeElement {
             htmlelement: HTMLElement::new_inherited(HTMLTimeElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTimeElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTimeElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTimeElement> {
+        let element = HTMLTimeElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTimeElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmltitleelement.rs b/src/components/script/dom/htmltitleelement.rs
index b6466637181..61eebf793a5 100644
--- a/src/components/script/dom/htmltitleelement.rs
+++ b/src/components/script/dom/htmltitleelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTitleElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLTitleElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLTitleElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTitleElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLTitleElementDerived for EventTarget {
+    fn is_htmltitleelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTitleElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTitleElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTitleElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTitleElement {
         HTMLTitleElement {
             htmlelement: HTMLElement::new_inherited(HTMLTitleElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTitleElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTitleElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTitleElement> {
+        let element = HTMLTitleElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTitleElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmltrackelement.rs b/src/components/script/dom/htmltrackelement.rs
index bf081d44918..24fcb38dd12 100644
--- a/src/components/script/dom/htmltrackelement.rs
+++ b/src/components/script/dom/htmltrackelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLTrackElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLTrackElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLTrackElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLTrackElement {
     htmlelement: HTMLElement,
 }
 
+impl HTMLTrackElementDerived for EventTarget {
+    fn is_htmltrackelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLTrackElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLTrackElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLTrackElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLTrackElement {
         HTMLTrackElement {
             htmlelement: HTMLElement::new_inherited(HTMLTrackElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLTrackElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLTrackElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLTrackElement> {
+        let element = HTMLTrackElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLTrackElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlulistelement.rs b/src/components/script/dom/htmlulistelement.rs
index 812144edf57..3533632b8a2 100644
--- a/src/components/script/dom/htmlulistelement.rs
+++ b/src/components/script/dom/htmlulistelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLUListElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLUListElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLUListElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLUListElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLUListElementDerived for EventTarget {
+    fn is_htmlulistelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLUListElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLUListElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLUListElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLUListElement {
         HTMLUListElement {
             htmlelement: HTMLElement::new_inherited(HTMLUListElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLUListElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLUListElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLUListElement> {
+        let element = HTMLUListElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLUListElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/htmlunknownelement.rs b/src/components/script/dom/htmlunknownelement.rs
index 67aa56bc47c..3c353acdb25 100644
--- a/src/components/script/dom/htmlunknownelement.rs
+++ b/src/components/script/dom/htmlunknownelement.rs
@@ -3,25 +3,38 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLUnknownElementBinding;
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::HTMLUnknownElementDerived;
+use dom::bindings::js::JS;
+use dom::document::Document;
 use dom::element::HTMLUnknownElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLUnknownElement {
     htmlelement: HTMLElement
 }
 
+impl HTMLUnknownElementDerived for EventTarget {
+    fn is_htmlunknownelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLUnknownElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLUnknownElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLUnknownElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLUnknownElement {
         HTMLUnknownElement {
             htmlelement: HTMLElement::new_inherited(HTMLUnknownElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLUnknownElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLUnknownElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLUnknownElement> {
+        let element = HTMLUnknownElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLUnknownElementBinding::Wrap)
     }
 }
diff --git a/src/components/script/dom/htmlvideoelement.rs b/src/components/script/dom/htmlvideoelement.rs
index c3c1ac9a9b4..437e3f8bfc1 100644
--- a/src/components/script/dom/htmlvideoelement.rs
+++ b/src/components/script/dom/htmlvideoelement.rs
@@ -3,27 +3,40 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::HTMLVideoElementBinding;
+use dom::bindings::codegen::InheritTypes::HTMLVideoElementDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::ErrorResult;
-use dom::document::AbstractDocument;
+use dom::document::Document;
 use dom::element::HTMLVideoElementTypeId;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlmediaelement::HTMLMediaElement;
-use dom::node::{AbstractNode, Node};
+use dom::node::{Node, ElementNodeTypeId};
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct HTMLVideoElement {
     htmlmediaelement: HTMLMediaElement
 }
 
+impl HTMLVideoElementDerived for EventTarget {
+    fn is_htmlvideoelement(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ElementNodeTypeId(HTMLVideoElementTypeId)) => true,
+            _ => false
+        }
+    }
+}
+
 impl HTMLVideoElement {
-    pub fn new_inherited(localName: DOMString, document: AbstractDocument) -> HTMLVideoElement {
+    pub fn new_inherited(localName: DOMString, document: JS<Document>) -> HTMLVideoElement {
         HTMLVideoElement {
             htmlmediaelement: HTMLMediaElement::new_inherited(HTMLVideoElementTypeId, localName, document)
         }
     }
 
-    pub fn new(localName: DOMString, document: AbstractDocument) -> AbstractNode {
-        let element = HTMLVideoElement::new_inherited(localName, document);
-        Node::reflect_node(@mut element, document, HTMLVideoElementBinding::Wrap)
+    pub fn new(localName: DOMString, document: &JS<Document>) -> JS<HTMLVideoElement> {
+        let element = HTMLVideoElement::new_inherited(localName, document.clone());
+        Node::reflect_node(~element, document, HTMLVideoElementBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/location.rs b/src/components/script/dom/location.rs
index b59248346e5..442373fea90 100644
--- a/src/components/script/dom/location.rs
+++ b/src/components/script/dom/location.rs
@@ -2,17 +2,19 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::codegen::LocationBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::utils::Fallible;
-use dom::bindings::codegen::LocationBinding;
 use dom::window::Window;
 use servo_util::str::DOMString;
 
 use script_task::{Page};
 
+#[deriving(Encodable)]
 pub struct Location {
     reflector_: Reflector, //XXXjdm cycle: window->Location->window
-    page: @mut Page
+    page: @mut Page,
 }
 
 impl Location {
@@ -23,8 +25,10 @@ impl Location {
         }
     }
 
-    pub fn new(window: &Window, page: @mut Page) -> @mut Location {
-        reflect_dom_object(@mut Location::new_inherited(page), window, LocationBinding::Wrap)
+    pub fn new(window: &Window, page: @mut Page) -> JS<Location> {
+        reflect_dom_object(~Location::new_inherited(page),
+                           window,
+                           LocationBinding::Wrap)
     }
 
     pub fn Assign(&self, _url: DOMString) {
diff --git a/src/components/script/dom/mouseevent.rs b/src/components/script/dom/mouseevent.rs
index c61c5c1aee0..7f840877b30 100644
--- a/src/components/script/dom/mouseevent.rs
+++ b/src/components/script/dom/mouseevent.rs
@@ -3,17 +3,20 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::MouseEventBinding;
+use dom::bindings::codegen::InheritTypes::MouseEventDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{ErrorResult, Fallible};
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
-use dom::event::{AbstractEvent, Event, MouseEventTypeId};
-use dom::eventtarget::AbstractEventTarget;
+use dom::event::{Event, MouseEventTypeId};
+use dom::eventtarget::EventTarget;
 use dom::uievent::UIEvent;
 use dom::window::Window;
 use dom::windowproxy::WindowProxy;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct MouseEvent {
-    parent: UIEvent,
+    mouseevent: UIEvent,
     screen_x: i32,
     screen_y: i32,
     client_x: i32,
@@ -23,13 +26,19 @@ pub struct MouseEvent {
     alt_key: bool,
     meta_key: bool,
     button: u16,
-    related_target: Option<AbstractEventTarget>
+    related_target: Option<JS<EventTarget>>
+}
+
+impl MouseEventDerived for Event {
+    fn is_mouseevent(&self) -> bool {
+        self.type_id == MouseEventTypeId
+    }
 }
 
 impl MouseEvent {
     pub fn new_inherited() -> MouseEvent {
         MouseEvent {
-            parent: UIEvent::new_inherited(MouseEventTypeId),
+            mouseevent: UIEvent::new_inherited(MouseEventTypeId),
             screen_x: 0,
             screen_y: 0,
             client_x: 0,
@@ -43,21 +52,21 @@ impl MouseEvent {
         }
     }
 
-    pub fn new(window: @mut Window) -> AbstractEvent {
-        Event::as_abstract(reflect_dom_object(@mut MouseEvent::new_inherited(),
-                                              window,
-                                              MouseEventBinding::Wrap))
+    pub fn new(window: &JS<Window>) -> JS<MouseEvent> {
+        reflect_dom_object(~MouseEvent::new_inherited(),
+                           window.get(),
+                           MouseEventBinding::Wrap)
     }
 
-    pub fn Constructor(owner: @mut Window,
+    pub fn Constructor(owner: &JS<Window>,
                        type_: DOMString,
-                       init: &MouseEventBinding::MouseEventInit) -> Fallible<AbstractEvent> {
-        let ev = MouseEvent::new(owner);
-        ev.mut_mouseevent().InitMouseEvent(type_, init.bubbles, init.cancelable, init.view,
-                                           init.detail, init.screenX, init.screenY,
-                                           init.clientX, init.clientY, init.ctrlKey,
-                                           init.altKey, init.shiftKey, init.metaKey,
-                                           init.button, init.relatedTarget);
+                       init: &MouseEventBinding::MouseEventInit) -> Fallible<JS<MouseEvent>> {
+        let mut ev = MouseEvent::new(owner);
+        ev.get_mut().InitMouseEvent(type_, init.bubbles, init.cancelable, init.view.clone(),
+                                      init.detail, init.screenX, init.screenY,
+                                      init.clientX, init.clientY, init.ctrlKey,
+                                      init.altKey, init.shiftKey, init.metaKey,
+                                      init.button, init.relatedTarget.clone());
         Ok(ev)
     }
 
@@ -102,8 +111,8 @@ impl MouseEvent {
         0
     }
 
-    pub fn GetRelatedTarget(&self) -> Option<AbstractEventTarget> {
-        self.related_target
+    pub fn GetRelatedTarget(&self) -> Option<JS<EventTarget>> {
+        self.related_target.clone()
     }
 
     pub fn GetModifierState(&self, _keyArg: DOMString) -> bool {
@@ -115,7 +124,7 @@ impl MouseEvent {
                           typeArg: DOMString,
                           canBubbleArg: bool,
                           cancelableArg: bool,
-                          viewArg: Option<@mut WindowProxy>,
+                          viewArg: Option<JS<WindowProxy>>,
                           detailArg: i32,
                           screenXArg: i32,
                           screenYArg: i32,
@@ -126,8 +135,8 @@ impl MouseEvent {
                           shiftKeyArg: bool,
                           metaKeyArg: bool,
                           buttonArg: u16,
-                          relatedTargetArg: Option<AbstractEventTarget>) -> ErrorResult {
-        self.parent.InitUIEvent(typeArg, canBubbleArg, cancelableArg, viewArg, detailArg);
+                          relatedTargetArg: Option<JS<EventTarget>>) -> ErrorResult {
+        self.mouseevent.InitUIEvent(typeArg, canBubbleArg, cancelableArg, viewArg, detailArg);
         self.screen_x = screenXArg;
         self.screen_y = screenYArg;
         self.client_x = clientXArg;
@@ -144,10 +153,10 @@ impl MouseEvent {
 
 impl Reflectable for MouseEvent {
     fn reflector<'a>(&'a self) -> &'a Reflector {
-        self.parent.reflector()
+        self.mouseevent.reflector()
     }
 
     fn mut_reflector<'a>(&'a mut self) -> &'a mut Reflector {
-        self.parent.mut_reflector()
+        self.mouseevent.mut_reflector()
     }
 }
diff --git a/src/components/script/dom/navigator.rs b/src/components/script/dom/navigator.rs
index 0c011f9bd58..693e86cb23d 100644
--- a/src/components/script/dom/navigator.rs
+++ b/src/components/script/dom/navigator.rs
@@ -2,12 +2,14 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::codegen::NavigatorBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::utils::Fallible;
-use dom::bindings::codegen::NavigatorBinding;
 use dom::window::Window;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct Navigator {
     reflector_: Reflector //XXXjdm cycle: window->navigator->window
 }
@@ -19,8 +21,10 @@ impl Navigator {
         }
     }
 
-    pub fn new(window: &Window) -> @mut Navigator {
-        reflect_dom_object(@mut Navigator::new_inherited(), window, NavigatorBinding::Wrap)
+    pub fn new(window: &Window) -> JS<Navigator> {
+        reflect_dom_object(~Navigator::new_inherited(),
+                           window,
+                           NavigatorBinding::Wrap)
     }
 
     pub fn DoNotTrack(&self) -> DOMString {
diff --git a/src/components/script/dom/node.rs b/src/components/script/dom/node.rs
index 3f0649fbdac..a0357c92ab4 100644
--- a/src/components/script/dom/node.rs
+++ b/src/components/script/dom/node.rs
@@ -4,22 +4,23 @@
 
 //! The core DOM types. Defines the basic DOM hierarchy as well as all the HTML elements.
 
+use dom::bindings::codegen::InheritTypes::{DocumentTypeCast, ElementCast, TextCast, NodeCast};
+use dom::bindings::codegen::InheritTypes::{CharacterDataCast, NodeBase, NodeDerived};
+use dom::bindings::codegen::InheritTypes::ProcessingInstructionCast;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::utils::{ErrorResult, Fallible, NotFound, HierarchyRequest};
 use dom::bindings::utils;
 use dom::characterdata::CharacterData;
-use dom::document::{AbstractDocument, DocumentTypeId};
+use dom::document::Document;
 use dom::documenttype::DocumentType;
-use dom::element::{Element, ElementTypeId, HTMLImageElementTypeId, HTMLIframeElementTypeId, HTMLObjectElementTypeId};
-use dom::element::{HTMLAnchorElementTypeId, HTMLStyleElementTypeId};
-use dom::eventtarget::{AbstractEventTarget, EventTarget, NodeTypeId};
-use dom::htmliframeelement::HTMLIFrameElement;
-use dom::htmlimageelement::HTMLImageElement;
-use dom::htmlobjectelement::HTMLObjectElement;
+use dom::element::{Element, ElementTypeId, HTMLAnchorElementTypeId};
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::nodelist::{NodeList};
 use dom::text::Text;
 use dom::processinginstruction::ProcessingInstruction;
 use layout_interface::{LayoutChan, ReapLayoutDataMsg, UntrustedNodeAddress};
+use layout_interface::TrustedNodeAddress;
 use servo_util::str::{DOMString, null_str_as_empty};
 
 use js::jsapi::{JSContext, JSObject, JSRuntime};
@@ -27,25 +28,19 @@ use js::jsfriendapi;
 use std::cast::transmute;
 use std::cast;
 use std::cell::{RefCell, Ref, RefMut};
-use std::iter::Filter;
+use std::iter::{Map, Filter};
 use std::libc::uintptr_t;
-use std::util;
 use std::unstable::raw::Box;
+use std::util;
+
+use extra::serialize::{Encoder, Encodable};
 
 //
 // The basic Node structure
 //
 
-/// This is what a Node looks like if you do not know what kind of node it is. To unpack it, use
-/// downcast().
-///
-/// FIXME: This should be replaced with a trait once they can inherit from structs.
-#[deriving(Eq)]
-pub struct AbstractNode {
-    priv obj: *mut (),
-}
-
 /// An HTML node.
+#[deriving(Encodable)]
 pub struct Node {
     /// The JavaScript reflector for this node.
     eventtarget: EventTarget,
@@ -53,28 +48,26 @@ pub struct Node {
     /// The type of node that this is.
     type_id: NodeTypeId,
 
-    abstract: Option<AbstractNode>,
-
     /// The parent of this node.
-    parent_node: Option<AbstractNode>,
+    parent_node: Option<JS<Node>>,
 
     /// The first child of this node.
-    first_child: Option<AbstractNode>,
+    first_child: Option<JS<Node>>,
 
     /// The last child of this node.
-    last_child: Option<AbstractNode>,
+    last_child: Option<JS<Node>>,
 
     /// The next sibling of this node.
-    next_sibling: Option<AbstractNode>,
+    next_sibling: Option<JS<Node>>,
 
     /// The previous sibling of this node.
-    prev_sibling: Option<AbstractNode>,
+    prev_sibling: Option<JS<Node>>,
 
     /// The document that this node belongs to.
-    priv owner_doc: Option<AbstractDocument>,
+    priv owner_doc: Option<JS<Document>>,
 
     /// The live list of children return by .childNodes.
-    child_list: Option<@mut NodeList>,
+    child_list: Option<JS<NodeList>>,
 
     /// A bitfield of flags for node items.
     priv flags: NodeFlags,
@@ -86,14 +79,29 @@ pub struct Node {
     layout_data: LayoutDataRef,
 }
 
+impl<S: Encoder> Encodable<S> for LayoutDataRef {
+    fn encode(&self, _s: &mut S) {
+    }
+}
+
+impl NodeDerived for EventTarget {
+    fn is_node(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(_) => true,
+            _ => false
+        }
+    }
+}
+
 /// Flags for node items.
+#[deriving(Encodable)]
 pub struct NodeFlags(u8);
 
 impl NodeFlags {
     pub fn new(type_id: NodeTypeId) -> NodeFlags {
         let mut flags = NodeFlags(0);
         match type_id {
-            DocumentNodeTypeId(_) => { flags.set_is_in_doc(true); }
+            DocumentNodeTypeId => { flags.set_is_in_doc(true); }
             _ => {}
         }
         flags
@@ -195,424 +203,220 @@ impl LayoutDataRef {
 pub trait TLayoutData {}
 
 /// The different types of nodes.
-#[deriving(Eq)]
+#[deriving(Eq,Encodable)]
 pub enum NodeTypeId {
     DoctypeNodeTypeId,
     DocumentFragmentNodeTypeId,
     CommentNodeTypeId,
-    DocumentNodeTypeId(DocumentTypeId),
+    DocumentNodeTypeId,
     ElementNodeTypeId(ElementTypeId),
     TextNodeTypeId,
     ProcessingInstructionNodeTypeId,
 }
 
-impl Clone for AbstractNode {
-    fn clone(&self) -> AbstractNode {
-        *self
-    }
+pub trait INode {
+    fn AppendChild(&mut self, node: &mut JS<Node>) -> Fallible<JS<Node>>;
+    fn ReplaceChild(&mut self, node: &mut JS<Node>, child: &mut JS<Node>) -> Fallible<JS<Node>>;
+    fn RemoveChild(&mut self, node: &mut JS<Node>) -> Fallible<JS<Node>>;
 }
 
-impl AbstractNode {
-    #[inline]
-    pub fn node<'a>(&'a self) -> &'a Node {
-        unsafe {
-            let box_: *mut Box<Node> = cast::transmute(self.obj);
-            &(*box_).data
-        }
+impl INode for JS<Node> {
+    fn AppendChild(&mut self, node: &mut JS<Node>) -> Fallible<JS<Node>> {
+        let mut self_node = self.clone();
+        self.get_mut().AppendChild(&mut self_node, node)
     }
 
-    #[inline]
-    pub fn mut_node<'a>(&'a self) -> &'a mut Node {
-        unsafe {
-            let box_: *mut Box<Node> = cast::transmute(self.obj);
-            &mut (*box_).data
-        }
-    }
-
-    #[inline]
-    pub fn parent_node(&self) -> Option<AbstractNode> {
-        self.node().parent_node
+    fn ReplaceChild(&mut self, node: &mut JS<Node>, child: &mut JS<Node>) -> Fallible<JS<Node>> {
+        let mut self_node = self.clone();
+        self.get_mut().ReplaceChild(&mut self_node, node, child)
     }
 
-    #[inline]
-    pub fn first_child(&self) -> Option<AbstractNode> {
-        self.node().first_child
-    }
-
-    #[inline]
-    pub fn last_child(&self) -> Option<AbstractNode> {
-        self.node().last_child
-    }
-
-    pub fn is_element(&self) -> bool {
-        match self.type_id() {
-            ElementNodeTypeId(..) => true,
-            _ => false
-        }
-    }
-
-    pub fn is_document(&self) -> bool {
-        match self.type_id() {
-            DocumentNodeTypeId(..) => true,
-            _ => false
-        }
-    }
-
-    /// If the given untrusted node address represents a valid DOM node in the given runtime,
-    /// returns it.
-    pub fn from_untrusted_node_address(runtime: *JSRuntime, candidate: UntrustedNodeAddress)
-                                       -> AbstractNode {
-        unsafe {
-            let candidate: uintptr_t = cast::transmute(candidate);
-            let object: *JSObject = jsfriendapi::bindgen::JS_GetAddressableObject(runtime,
-                                                                                  candidate);
-            if object.is_null() {
-                fail!("Attempted to create an `AbstractNode` from an invalid pointer!")
-            }
-            let boxed_node: *mut Box<Node> = utils::unwrap(object);
-            AbstractNode::from_box(boxed_node)
-        }
-    }
-
-    pub fn is_inclusive_ancestor_of(&self, parent: AbstractNode) -> bool {
-        *self == parent || parent.ancestors().any(|ancestor| ancestor == *self)
-    }
-
-    pub fn is_parent_of(&self, child: AbstractNode) -> bool {
-        child.parent_node() == Some(*self)
+    fn RemoveChild(&mut self, node: &mut JS<Node>) -> Fallible<JS<Node>> {
+        let mut self_node = self.clone();
+        self.get_mut().RemoveChild(&mut self_node, node)
     }
 }
 
-impl<'a> AbstractNode {
-    // Unsafe accessors
+pub trait NodeHelpers {
+    fn ancestors(&self) -> AncestorIterator;
+    fn children(&self) -> AbstractNodeChildrenIterator;
+    fn child_elements(&self) -> ChildElementIterator;
+    fn following_siblings(&self) -> AbstractNodeChildrenIterator;
+    fn is_in_doc(&self) -> bool;
+    fn is_inclusive_ancestor_of(&self, parent: &JS<Node>) -> bool;
+    fn is_parent_of(&self, child: &JS<Node>) -> bool;
+
+    fn type_id(&self) -> NodeTypeId;
+
+    fn parent_node(&self) -> Option<JS<Node>>;
+    fn first_child(&self) -> Option<JS<Node>>;
+    fn last_child(&self) -> Option<JS<Node>>;
+    fn prev_sibling(&self) -> Option<JS<Node>>;
+    fn next_sibling(&self) -> Option<JS<Node>>;
+
+    fn is_element(&self) -> bool;
+    fn is_document(&self) -> bool;
+    fn is_doctype(&self) -> bool;
+    fn is_text(&self) -> bool;
+    fn is_anchor_element(&self) -> bool;
+
+    fn node_inserted(&self);
+    fn node_removed(&self);
+    fn add_child(&mut self, new_child: &mut JS<Node>, before: Option<JS<Node>>);
+    fn remove_child(&mut self, child: &mut JS<Node>);
+
+    fn get_hover_state(&self) -> bool;
+    fn set_hover_state(&mut self, state: bool);
+
+    fn dump(&self);
+    fn dump_indent(&self, indent: uint);
+    fn debug_str(&self) -> ~str;
+
+    fn traverse_preorder(&self) -> TreeIterator;
+    fn sequential_traverse_postorder(&self) -> TreeIterator;
+    fn inclusively_following_siblings(&self) -> AbstractNodeChildrenIterator;
+
+    fn from_untrusted_node_address(runtime: *JSRuntime, candidate: UntrustedNodeAddress) -> Self;
+    fn to_trusted_node_address(&self) -> TrustedNodeAddress;
+}
 
-    pub unsafe fn as_cacheable_wrapper(&self) -> @mut Reflectable {
-        match self.type_id() {
-            TextNodeTypeId => {
-                let node: @mut Text = cast::transmute(self.obj);
-                node as @mut Reflectable
-            }
-            _ => {
-                fail!("unsupported node type")
-            }
-        }
+impl NodeHelpers for JS<Node> {
+    /// Dumps the subtree rooted at this node, for debugging.
+    fn dump(&self) {
+        self.dump_indent(0);
     }
 
-    /// Allow consumers to recreate an AbstractNode from the raw boxed type.
-    /// Must only be used in situations where the boxed type is in the inheritance
-    /// chain for nodes.
-    ///
-    /// FIXME(pcwalton): Mark unsafe?
-    pub fn from_box<T>(ptr: *mut Box<T>) -> AbstractNode {
-        AbstractNode {
-            obj: ptr as *mut ()
+    /// Dumps the node tree, for debugging, with indentation.
+    fn dump_indent(&self, indent: uint) {
+        let mut s = ~"";
+        for _ in range(0, indent) {
+            s.push_str("    ");
         }
-    }
 
-    /// Allow consumers to upcast from derived classes.
-    pub fn from_document(doc: AbstractDocument) -> AbstractNode {
-        unsafe {
-            cast::transmute(doc)
-        }
-    }
+        s.push_str(self.debug_str());
+        debug!("{:s}", s);
 
-    pub fn from_eventtarget(target: AbstractEventTarget) -> AbstractNode {
-        assert!(target.is_node());
-        unsafe {
-            cast::transmute(target)
+        // FIXME: this should have a pure version?
+        for kid in self.children() {
+            kid.dump_indent(indent + 1u)
         }
     }
 
-    // Convenience accessors
-
-    /// Returns the type ID of this node. Fails if this node is borrowed mutably.
-    #[inline]
-    pub fn type_id(self) -> NodeTypeId {
-        self.node().type_id
+    /// Returns a string that describes this node.
+    fn debug_str(&self) -> ~str {
+        format!("{:?}", self.type_id())
     }
 
-    /// Returns the previous sibling of this node. Fails if this node is borrowed mutably.
-    pub fn prev_sibling(self) -> Option<AbstractNode> {
-        self.node().prev_sibling
+    /// Iterates over all ancestors of this node.
+    fn ancestors(&self) -> AncestorIterator {
+        self.get().ancestors()
     }
 
-    /// Returns the next sibling of this node. Fails if this node is borrowed mutably.
-    pub fn next_sibling(self) -> Option<AbstractNode> {
-        self.node().next_sibling
+    fn children(&self) -> AbstractNodeChildrenIterator {
+        self.get().children()
     }
 
-    //
-    // Downcasting borrows
-    //
-
-    pub fn transmute<'a, T, R>(self, f: |&'a T| -> R) -> R {
-        unsafe {
-            let node_box: *mut Box<Node> = transmute(self.obj);
-            let node = &mut (*node_box).data;
-            let old = node.abstract;
-            node.abstract = Some(self);
-            let box_: *Box<T> = transmute(self.obj);
-            let rv = f(&(*box_).data);
-            node.abstract = old;
-            rv
-        }
+    fn child_elements(&self) -> ChildElementIterator {
+        self.get().child_elements()
     }
 
-    pub fn transmute_mut<T, R>(self, f: |&mut T| -> R) -> R {
-        unsafe {
-            let node_box: *mut Box<Node> = transmute(self.obj);
-            let node = &mut (*node_box).data;
-            let old = node.abstract;
-            node.abstract = Some(self);
-            let box_: *Box<T> = transmute(self.obj);
-            let rv = f(cast::transmute(&(*box_).data));
-            node.abstract = old;
-            rv
-        }
+    fn is_in_doc(&self) -> bool {
+        self.get().flags.is_in_doc()
     }
 
-    // FIXME: This should be doing dynamic borrow checking for safety.
-    pub fn is_characterdata(self) -> bool {
-        self.is_text() || self.is_comment() || self.is_processing_instruction()
+    /// Returns the type ID of this node. Fails if this node is borrowed mutably.
+    fn type_id(&self) -> NodeTypeId {
+        self.get().type_id
     }
 
-    pub fn with_imm_characterdata<R>(self, f: |&CharacterData| -> R) -> R {
-        if !self.is_characterdata() {
-            fail!(~"node is not characterdata");
-        }
-        self.transmute(f)
+    fn parent_node(&self) -> Option<JS<Node>> {
+        self.get().parent_node.clone()
     }
 
-    pub fn with_mut_characterdata<R>(self, f: |&mut CharacterData| -> R) -> R {
-        if !self.is_characterdata() {
-            fail!(~"node is not characterdata");
-        }
-        self.transmute_mut(f)
+    fn first_child(&self) -> Option<JS<Node>> {
+        self.get().first_child.clone()
     }
 
-    pub fn is_doctype(self) -> bool {
-        self.type_id() == DoctypeNodeTypeId
+    fn last_child(&self) -> Option<JS<Node>> {
+        self.get().last_child.clone()
     }
 
-    pub fn with_imm_doctype<R>(self, f: |&DocumentType| -> R) -> R {
-        if !self.is_doctype() {
-            fail!(~"node is not doctype");
-        }
-        self.transmute(f)
+    /// Returns the previous sibling of this node. Fails if this node is borrowed mutably.
+    fn prev_sibling(&self) -> Option<JS<Node>> {
+        self.get().prev_sibling.clone()
     }
 
-    pub fn with_mut_doctype<R>(self, f: |&mut DocumentType| -> R) -> R {
-        if !self.is_doctype() {
-            fail!(~"node is not doctype");
-        }
-        self.transmute_mut(f)
+    /// Returns the next sibling of this node. Fails if this node is borrowed mutably.
+    fn next_sibling(&self) -> Option<JS<Node>> {
+        self.get().next_sibling.clone()
     }
 
     #[inline]
-    pub fn is_comment(self) -> bool {
-        // FIXME(pcwalton): Temporary workaround for the lack of inlining of autogenerated `Eq`
-        // implementations in Rust.
+    fn is_element(&self) -> bool {
         match self.type_id() {
-            CommentNodeTypeId => true,
-            _ => false,
+            ElementNodeTypeId(..) => true,
+            _ => false
         }
     }
 
     #[inline]
-    pub fn is_text(self) -> bool {
-        // FIXME(pcwalton): Temporary workaround for the lack of inlining of autogenerated `Eq`
-        // implementations in Rust.
+    fn is_document(&self) -> bool {
         match self.type_id() {
-            TextNodeTypeId => true,
-            _ => false,
-        }
-    }
-
-    pub fn with_imm_text<R>(self, f: |&Text| -> R) -> R {
-        if !self.is_text() {
-            fail!(~"node is not text");
-        }
-        self.transmute(f)
-    }
-
-    pub fn with_mut_text<R>(self, f: |&mut Text| -> R) -> R {
-        if !self.is_text() {
-            fail!(~"node is not text");
+            DocumentNodeTypeId => true,
+            _ => false
         }
-        self.transmute_mut(f)
     }
 
     #[inline]
-    pub fn is_processing_instruction(self) -> bool {
-        self.type_id() == ProcessingInstructionNodeTypeId
-    }
-
-    pub fn with_imm_processing_instruction<R>(self, f: |&ProcessingInstruction| -> R)  -> R {
-        if !self.is_processing_instruction() {
-            fail!("node is not processing instruction");
-        }
-        self.transmute(f)
-    }
-
-    // FIXME: This should be doing dynamic borrow checking for safety.
-    pub fn with_imm_element<R>(self, f: |&Element| -> R) -> R {
-        if !self.is_element() {
-            fail!(~"node is not an element");
-        }
-        self.transmute(f)
-    }
-
-    // FIXME: This should be doing dynamic borrow checking for safety.
-    pub fn as_mut_element<R>(self, f: |&mut Element| -> R) -> R {
-        if !self.is_element() {
-            fail!(~"node is not an element");
+    fn is_anchor_element(&self) -> bool {
+        match self.type_id() {
+            ElementNodeTypeId(HTMLAnchorElementTypeId) => true,
+            _ => false
         }
-        self.transmute_mut(f)
     }
 
     #[inline]
-    pub fn is_image_element(self) -> bool {
+    fn is_doctype(&self) -> bool {
         match self.type_id() {
-            ElementNodeTypeId(HTMLImageElementTypeId) => true,
-            _ => false,
-        }
-    }
-
-    pub fn with_mut_image_element<R>(self, f: |&mut HTMLImageElement| -> R) -> R {
-        if !self.is_image_element() {
-            fail!(~"node is not an image element");
+            DoctypeNodeTypeId => true,
+            _ => false
         }
-        self.transmute_mut(f)
-    }
-
-    pub fn is_iframe_element(self) -> bool {
-        self.type_id() == ElementNodeTypeId(HTMLIframeElementTypeId)
     }
 
     #[inline]
-    pub fn is_object_element(self) -> bool {
-        self.type_id() == ElementNodeTypeId(HTMLObjectElementTypeId)
-    }
-
-    pub fn with_mut_object_element<R>(self, f: |&mut HTMLObjectElement| -> R) -> R {
-        if !self.is_object_element() {
-            fail!(~"node is not an image element");
-        }
-        self.transmute_mut(f)
-    }
-
-    pub fn with_mut_iframe_element<R>(self, f: |&mut HTMLIFrameElement| -> R) -> R {
-        if !self.is_iframe_element() {
-            fail!(~"node is not an iframe element");
-        }
-        self.transmute_mut(f)
-    }
-
-    pub fn is_style_element(self) -> bool {
-        self.type_id() == ElementNodeTypeId(HTMLStyleElementTypeId)
-    }
-
-    pub fn is_anchor_element(self) -> bool {
-        self.type_id() == ElementNodeTypeId(HTMLAnchorElementTypeId)
-    }
-
-    pub unsafe fn raw_object(self) -> *mut Box<Node> {
-        cast::transmute(self.obj)
-    }
-
-    pub fn from_raw(raw: *mut Box<Node>) -> AbstractNode {
-        AbstractNode {
-            obj: raw as *mut ()
-        }
-    }
-
-    /// Dumps the subtree rooted at this node, for debugging.
-    pub fn dump(&self) {
-        self.dump_indent(0);
-    }
-
-    /// Dumps the node tree, for debugging, with indentation.
-    pub fn dump_indent(&self, indent: uint) {
-        let mut s = ~"";
-        for _ in range(0, indent) {
-            s.push_str("    ");
-        }
-
-        s.push_str(self.debug_str());
-        debug!("{:s}", s);
-
-        // FIXME: this should have a pure version?
-        for kid in self.children() {
-            kid.dump_indent(indent + 1u)
+    fn is_text(&self) -> bool {
+        // FIXME(pcwalton): Temporary workaround for the lack of inlining of autogenerated `Eq`
+        // implementations in Rust.
+        match self.type_id() {
+            TextNodeTypeId => true,
+            _ => false
         }
     }
 
-    /// Returns a string that describes this node.
-    pub fn debug_str(&self) -> ~str {
-        format!("{:?}", self.type_id())
-    }
-
-    //
-    // Convenience accessors
-    //
-
-    pub fn children(&self) -> AbstractNodeChildrenIterator {
-        self.node().children()
-    }
-
-    pub fn child_elements(&self) -> Filter<AbstractNode, AbstractNodeChildrenIterator> {
-        self.node().child_elements()
-    }
-
-    pub fn is_in_doc(&self) -> bool {
-        self.node().flags.is_in_doc()
-    }
-
-    pub fn get_hover_state(&self) -> bool {
-        self.node().flags.get_in_hover_state()
-    }
-
-    pub fn set_hover_state(&self, state: bool) {
-        self.mut_node().flags.set_is_in_hover_state(state);
-    }
-}
-
-impl AbstractNode {
-    // http://dom.spec.whatwg.org/#dom-node-appendchild
-    pub fn AppendChild(self, node: AbstractNode) -> Fallible<AbstractNode> {
-        self.node().AppendChild(self, node)
-    }
-
-    // http://dom.spec.whatwg.org/#dom-node-replacechild
-    pub fn ReplaceChild(self, node: AbstractNode, child: AbstractNode) -> Fallible<AbstractNode> {
-        self.node().ReplaceChild(self, node, child)
-    }
-
-    // http://dom.spec.whatwg.org/#dom-node-removechild
-    pub fn RemoveChild(self, node: AbstractNode) -> Fallible<AbstractNode> {
-        self.node().RemoveChild(self, node)
-    }
-
     // http://dom.spec.whatwg.org/#node-is-inserted
-    fn node_inserted(self) {
+    fn node_inserted(&self) {
         assert!(self.parent_node().is_some());
-        let document = self.node().owner_doc();
+        let mut document = self.get().owner_doc();
 
         // Register elements having "id" attribute to the owner doc.
-        document.mut_document().register_nodes_with_id(&self);
+        if self.is_element() {
+            document.get_mut().register_nodes_with_id(&ElementCast::to(self));
+        }
 
-        document.document().content_changed();
+        document.get().content_changed();
     }
 
     // http://dom.spec.whatwg.org/#node-is-removed
-    fn node_removed(self) {
+    fn node_removed(&self) {
         assert!(self.parent_node().is_none());
-        let document = self.node().owner_doc();
+        let mut document = self.get().owner_doc();
 
         // Unregister elements having "id".
-        document.mut_document().unregister_nodes_with_id(&self);
+        if self.is_element() {
+            document.get_mut().unregister_nodes_with_id(&ElementCast::to(self));
+        }
 
-        document.document().content_changed();
+        document.get().content_changed();
     }
 
     //
@@ -622,71 +426,66 @@ impl AbstractNode {
     /// Adds a new child to the end of this node's list of children.
     ///
     /// Fails unless `new_child` is disconnected from the tree.
-    fn add_child(&self, new_child: AbstractNode, before: Option<AbstractNode>) {
-        let this_node = self.mut_node();
-        let new_child_node = new_child.mut_node();
-        assert!(new_child_node.parent_node.is_none());
-        assert!(new_child_node.prev_sibling.is_none());
-        assert!(new_child_node.next_sibling.is_none());
+    fn add_child(&mut self, new_child: &mut JS<Node>, before: Option<JS<Node>>) {
+        assert!(new_child.parent_node().is_none());
+        assert!(new_child.prev_sibling().is_none());
+        assert!(new_child.next_sibling().is_none());
         match before {
-            Some(before) => {
-                let before_node = before.mut_node();
+            Some(mut before) => {
                 // XXX Should assert that parent is self.
-                assert!(before_node.parent_node.is_some());
-                match before_node.prev_sibling {
+                assert!(before.parent_node().is_some());
+                match before.prev_sibling() {
                     None => {
                         // XXX Should assert that before is the first child of
                         //     self.
-                        this_node.set_first_child(Some(new_child.clone()));
+                        self.get_mut().set_first_child(Some(new_child.clone()));
                     },
-                    Some(prev_sibling) => {
-                        let prev_sibling_node = prev_sibling.mut_node();
-                        prev_sibling_node.set_next_sibling(Some(new_child.clone()));
-                        new_child_node.set_prev_sibling(Some(prev_sibling.clone()));
+                    Some(mut prev_sibling) => {
+                        prev_sibling.get_mut().set_next_sibling(Some(new_child.clone()));
+                        new_child.get_mut().set_prev_sibling(Some(prev_sibling.clone()));
                     },
                 }
-                before_node.set_prev_sibling(Some(new_child.clone()));
-                new_child_node.set_next_sibling(Some(before.clone()));
+                before.get_mut().set_prev_sibling(Some(new_child.clone()));
+                new_child.get_mut().set_next_sibling(Some(before.clone()));
             },
             None => {
-                match this_node.last_child {
-                    None => this_node.set_first_child(Some(new_child.clone())),
-                    Some(last_child) => {
-                        let last_child_node = last_child.mut_node();
-                        assert!(last_child_node.next_sibling.is_none());
-                        last_child_node.set_next_sibling(Some(new_child.clone()));
-                        new_child_node.set_prev_sibling(Some(last_child.clone()));
+                match self.last_child() {
+                    None => self.get_mut().set_first_child(Some(new_child.clone())),
+                    Some(mut last_child) => {
+                        assert!(last_child.next_sibling().is_none());
+                        last_child.get_mut().set_next_sibling(Some(new_child.clone()));
+                        new_child.get_mut().set_prev_sibling(Some(last_child.clone()));
                     }
                 }
 
-                this_node.set_last_child(Some(new_child.clone()));
+                self.get_mut().set_last_child(Some(new_child.clone()));
             },
         }
 
-        new_child_node.set_parent_node(Some((*self).clone()));
+        new_child.get_mut().set_parent_node(Some(self.clone()));
     }
 
     /// Removes the given child from this node's list of children.
     ///
     /// Fails unless `child` is a child of this node. (FIXME: This is not yet checked.)
-    fn remove_child(&self, child: AbstractNode) {
-        let this_node = self.mut_node();
-        let child_node = child.mut_node();
+    fn remove_child(&mut self, child: &mut JS<Node>) {
+        let this_node = self.get_mut();
+        let child_node = child.get_mut();
         assert!(child_node.parent_node.is_some());
 
         match child_node.prev_sibling {
-            None => this_node.set_first_child(child_node.next_sibling),
-            Some(prev_sibling) => {
-                let prev_sibling_node = prev_sibling.mut_node();
-                prev_sibling_node.set_next_sibling(child_node.next_sibling);
+            None => this_node.set_first_child(child_node.next_sibling.clone()),
+            Some(ref mut prev_sibling) => {
+                let prev_sibling_node = prev_sibling.get_mut();
+                prev_sibling_node.set_next_sibling(child_node.next_sibling.clone());
             }
         }
 
         match child_node.next_sibling {
-            None => this_node.set_last_child(child_node.prev_sibling),
-            Some(next_sibling) => {
-                let next_sibling_node = next_sibling.mut_node();
-                next_sibling_node.set_prev_sibling(child_node.prev_sibling);
+            None => this_node.set_last_child(child_node.prev_sibling.clone()),
+            Some(ref mut next_sibling) => {
+                let next_sibling_node = next_sibling.get_mut();
+                next_sibling_node.set_prev_sibling(child_node.prev_sibling.clone());
             }
         }
 
@@ -694,20 +493,89 @@ impl AbstractNode {
         child_node.set_next_sibling(None);
         child_node.set_parent_node(None);
     }
+
+    fn get_hover_state(&self) -> bool {
+        self.get().flags.get_in_hover_state()
+    }
+
+    fn set_hover_state(&mut self, state: bool) {
+        self.get_mut().flags.set_is_in_hover_state(state);
+    }
+
+    /// Iterates over this node and all its descendants, in preorder.
+    fn traverse_preorder(&self) -> TreeIterator {
+        let mut nodes = ~[];
+        gather_abstract_nodes(self, &mut nodes, false);
+        TreeIterator::new(nodes)
+    }
+
+    /// Iterates over this node and all its descendants, in postorder.
+    fn sequential_traverse_postorder(&self) -> TreeIterator {
+        let mut nodes = ~[];
+        gather_abstract_nodes(self, &mut nodes, true);
+        TreeIterator::new(nodes)
+    }
+
+    fn inclusively_following_siblings(&self) -> AbstractNodeChildrenIterator {
+        AbstractNodeChildrenIterator {
+            current_node: Some(self.clone()),
+        }
+    }
+
+    fn is_inclusive_ancestor_of(&self, parent: &JS<Node>) -> bool {
+        self == parent || parent.ancestors().any(|ancestor| ancestor == *self)
+    }
+
+    fn following_siblings(&self) -> AbstractNodeChildrenIterator {
+        AbstractNodeChildrenIterator {
+            current_node: self.next_sibling(),
+        }
+    }
+
+    fn is_parent_of(&self, child: &JS<Node>) -> bool {
+        match child.parent_node() {
+            Some(ref parent) if parent == self => true,
+            _ => false
+        }
+    }
+
+    /// If the given untrusted node address represents a valid DOM node in the given runtime,
+    /// returns it.
+    fn from_untrusted_node_address(runtime: *JSRuntime, candidate: UntrustedNodeAddress)
+        -> JS<Node> {
+        unsafe {
+            let candidate: uintptr_t = cast::transmute(candidate);
+            let object: *JSObject = jsfriendapi::bindgen::JS_GetAddressableObject(runtime,
+                                                                                  candidate);
+            if object.is_null() {
+                fail!("Attempted to create a `JS<Node>` from an invalid pointer!")
+            }
+            let boxed_node: *mut Box<Node> = utils::unwrap(object);
+            JS::from_box(boxed_node)
+        }
+    }
+
+    fn to_trusted_node_address(&self) -> TrustedNodeAddress {
+        self.get() as *Node as TrustedNodeAddress
+    }
 }
 
 //
 // Iteration and traversal
 //
 
+type ChildElementIterator<'a> = Map<'a, JS<Node>,
+                                    JS<Element>,
+                                    Filter<'a, JS<Node>, AbstractNodeChildrenIterator>>;
+
 pub struct AbstractNodeChildrenIterator {
-    priv current_node: Option<AbstractNode>,
+    priv current_node: Option<JS<Node>>,
 }
 
-impl Iterator<AbstractNode> for AbstractNodeChildrenIterator {
-    fn next(&mut self) -> Option<AbstractNode> {
-        let node = self.current_node;
-        self.current_node = self.current_node.and_then(|node| {
+impl Iterator<JS<Node>> for AbstractNodeChildrenIterator {
+    fn next(&mut self) -> Option<JS<Node>> {
+        let node = self.current_node.clone();
+        self.current_node = node.clone().and_then(|node| {
             node.next_sibling()
         });
         node
@@ -715,11 +583,11 @@ impl Iterator<AbstractNode> for AbstractNodeChildrenIterator {
 }
 
 pub struct AncestorIterator {
-    priv current: Option<AbstractNode>,
+    priv current: Option<JS<Node>>,
 }
 
-impl Iterator<AbstractNode> for AncestorIterator {
-    fn next(&mut self) -> Option<AbstractNode> {
+impl Iterator<JS<Node>> for AncestorIterator {
+    fn next(&mut self) -> Option<JS<Node>> {
         if self.current.is_none() {
             return None;
         }
@@ -734,12 +602,12 @@ impl Iterator<AbstractNode> for AncestorIterator {
 // FIXME: Do this without precomputing a vector of refs.
 // Easy for preorder; harder for postorder.
 pub struct TreeIterator {
-    priv nodes: ~[AbstractNode],
+    priv nodes: ~[JS<Node>],
     priv index: uint,
 }
 
 impl TreeIterator {
-    fn new(nodes: ~[AbstractNode]) -> TreeIterator {
+    fn new(nodes: ~[JS<Node>]) -> TreeIterator {
         TreeIterator {
             nodes: nodes,
             index: 0,
@@ -747,8 +615,8 @@ impl TreeIterator {
     }
 }
 
-impl Iterator<AbstractNode> for TreeIterator {
-    fn next(&mut self) -> Option<AbstractNode> {
+impl Iterator<JS<Node>> for TreeIterator {
+    fn next(&mut self) -> Option<JS<Node>> {
         if self.index >= self.nodes.len() {
             None
         } else {
@@ -760,15 +628,15 @@ impl Iterator<AbstractNode> for TreeIterator {
 }
 
 pub struct NodeIterator {
-    start_node: AbstractNode,
-    current_node: Option<AbstractNode>,
+    start_node: JS<Node>,
+    current_node: Option<JS<Node>>,
     depth: uint,
     priv include_start: bool,
     priv include_descendants_of_void: bool
 }
 
 impl NodeIterator {
-    pub fn new(start_node: AbstractNode, include_start: bool, include_descendants_of_void: bool) -> NodeIterator {
+    pub fn new(start_node: JS<Node>, include_start: bool, include_descendants_of_void: bool) -> NodeIterator {
         NodeIterator {
             start_node: start_node,
             current_node: None,
@@ -778,44 +646,42 @@ impl NodeIterator {
         }
     }
 
-    fn next_child(&self, node: AbstractNode) -> Option<AbstractNode> {
-        if !self.include_descendants_of_void &&
-           node.is_element() {
-            node.with_imm_element(|elem| {
-                if elem.is_void() {
-                    None
-                } else {
-                    node.first_child()
-                }
-            })
+    fn next_child(&self, node: &JS<Node>) -> Option<JS<Node>> {
+        if !self.include_descendants_of_void && node.is_element() {
+            let elem: JS<Element> = ElementCast::to(node);
+            if elem.get().is_void() {
+                None
+            } else {
+                node.first_child()
+            }
         } else {
             node.first_child()
         }
     }
 }
 
-impl Iterator<AbstractNode> for NodeIterator {
-    fn next(&mut self) -> Option<AbstractNode> {
+impl Iterator<JS<Node>> for NodeIterator {
+    fn next(&mut self) -> Option<JS<Node>> {
          self.current_node = match self.current_node {
             None => {
                 if self.include_start {
-                    Some(self.start_node)
+                    Some(self.start_node.clone())
                 } else {
-                    self.next_child(self.start_node)
+                    self.next_child(&self.start_node)
                 }
             },
-            Some(node) => {
+            Some(ref node) => {
                 match self.next_child(node) {
                     Some(child) => {
                         self.depth += 1;
-                        Some(child)
+                        Some(child.clone())
                     },
-                    None if node == self.start_node => None,
+                    None if node == &self.start_node => None,
                     None => {
                         match node.next_sibling() {
                             Some(sibling) => Some(sibling),
                             None => {
-                                let mut candidate = node;
+                                let mut candidate = node.clone();
                                 while candidate.next_sibling().is_none() {
                                     candidate = candidate.parent_node().expect("Got to root without reaching start node");
                                     self.depth -= 1;
@@ -834,11 +700,11 @@ impl Iterator<AbstractNode> for NodeIterator {
                 }
             }
         };
-        self.current_node
+        self.current_node.clone()
     }
 }
 
-fn gather_abstract_nodes(cur: &AbstractNode, refs: &mut ~[AbstractNode], postorder: bool) {
+fn gather_abstract_nodes(cur: &JS<Node>, refs: &mut ~[JS<Node>], postorder: bool) {
     if !postorder {
         refs.push(cur.clone());
     }
@@ -850,75 +716,48 @@ fn gather_abstract_nodes(cur: &AbstractNode, refs: &mut ~[AbstractNode], postord
     }
 }
 
-impl AbstractNode {
-    /// Iterates over all ancestors of this node.
+impl Node {
     pub fn ancestors(&self) -> AncestorIterator {
         AncestorIterator {
-            current: self.parent_node(),
-        }
-    }
-
-    pub fn inclusively_following_siblings(&self) -> AbstractNodeChildrenIterator {
-        AbstractNodeChildrenIterator {
-            current_node: Some(*self),
+            current: self.parent_node.clone(),
         }
     }
 
-    pub fn following_siblings(&self) -> AbstractNodeChildrenIterator {
-        AbstractNodeChildrenIterator {
-            current_node: self.next_sibling(),
-        }
-    }
-
-    /// Iterates over this node and all its descendants, in preorder.
-    pub fn traverse_preorder(&self) -> TreeIterator {
-        let mut nodes = ~[];
-        gather_abstract_nodes(self, &mut nodes, false);
-        TreeIterator::new(nodes)
-    }
-
-    /// Iterates over this node and all its descendants, in postorder.
-    pub fn sequential_traverse_postorder(&self) -> TreeIterator {
-        let mut nodes = ~[];
-        gather_abstract_nodes(self, &mut nodes, true);
-        TreeIterator::new(nodes)
-    }
-}
-
-impl Node {
-    pub fn owner_doc(&self) -> AbstractDocument {
-        self.owner_doc.unwrap()
+    pub fn owner_doc(&self) -> JS<Document> {
+        self.owner_doc.clone().unwrap()
     }
 
-    pub fn set_owner_doc(&mut self, document: AbstractDocument) {
-        self.owner_doc = Some(document);
+    pub fn set_owner_doc(&mut self, document: &JS<Document>) {
+        self.owner_doc = Some(document.clone());
     }
 
     pub fn children(&self) -> AbstractNodeChildrenIterator {
         AbstractNodeChildrenIterator {
-            current_node: self.first_child,
+            current_node: self.first_child.clone(),
         }
     }
 
-    pub fn child_elements(&self) -> Filter<AbstractNode, AbstractNodeChildrenIterator> {
-        self.children().filter(|node| node.is_element())
+    pub fn child_elements(&self) -> ChildElementIterator {
+        self.children()
+            .filter(|node| node.is_element())
+            .map(|node| {
+                let elem: JS<Element> = ElementCast::to(&node);
+                elem
+            })
     }
 
-    pub fn reflect_node<N: Reflectable>
-            (node:      @mut N,
-             document:  AbstractDocument,
-             wrap_fn:   extern "Rust" fn(*JSContext, *JSObject, @mut N) -> *JSObject)
-             -> AbstractNode {
+    pub fn reflect_node<N: Reflectable+NodeBase>
+            (node:      ~N,
+             document:  &JS<Document>,
+             wrap_fn:   extern "Rust" fn(*JSContext, *JSObject, ~N) -> *JSObject)
+             -> JS<N> {
         assert!(node.reflector().get_jsobject().is_null());
-        let node = reflect_dom_object(node, document.document().window, wrap_fn);
+        let node = reflect_dom_object(node, document.get().window.get(), wrap_fn);
         assert!(node.reflector().get_jsobject().is_not_null());
-        // JS owns the node now, so transmute_copy to not increase the refcount
-        AbstractNode {
-            obj: unsafe { cast::transmute_copy(&node) },
-        }
+        node
     }
 
-    pub fn new_inherited(type_id: NodeTypeId, doc: AbstractDocument) -> Node {
+    pub fn new_inherited(type_id: NodeTypeId, doc: JS<Document>) -> Node {
         Node::new_(type_id, Some(doc))
     }
 
@@ -926,13 +765,11 @@ impl Node {
         Node::new_(type_id, None)
     }
 
-    fn new_(type_id: NodeTypeId, doc: Option<AbstractDocument>) -> Node {
+    fn new_(type_id: NodeTypeId, doc: Option<JS<Document>>) -> Node {
         Node {
-            eventtarget: EventTarget::new_inherited(NodeTypeId),
+            eventtarget: EventTarget::new_inherited(NodeTargetTypeId(type_id)),
             type_id: type_id,
 
-            abstract: None,
-
             parent_node: None,
             first_child: None,
             last_child: None,
@@ -967,34 +804,32 @@ impl Node {
             TextNodeTypeId                  => 3,
             ProcessingInstructionNodeTypeId => 7,
             CommentNodeTypeId               => 8,
-            DocumentNodeTypeId(_)           => 9,
+            DocumentNodeTypeId              => 9,
             DoctypeNodeTypeId               => 10,
             DocumentFragmentNodeTypeId      => 11,
         }
     }
 
     // http://dom.spec.whatwg.org/#dom-node-nodename
-    pub fn NodeName(&self, abstract_self: AbstractNode) -> DOMString {
+    pub fn NodeName(&self, abstract_self: &JS<Node>) -> DOMString {
         match self.type_id {
             ElementNodeTypeId(..) => {
-                abstract_self.with_imm_element(|element| {
-                    element.TagName()
-                })
+                let elem: JS<Element> = ElementCast::to(abstract_self);
+                elem.get().TagName()
             }
             TextNodeTypeId => ~"#text",
             ProcessingInstructionNodeTypeId => {
-                abstract_self.with_imm_processing_instruction(|processing_instruction| {
-                    processing_instruction.Target()
-                })
+                let processing_instruction: JS<ProcessingInstruction> =
+                    ProcessingInstructionCast::to(abstract_self);
+                processing_instruction.get().Target()
             }
             CommentNodeTypeId => ~"#comment",
             DoctypeNodeTypeId => {
-                abstract_self.with_imm_doctype(|doctype| {
-                    doctype.name.clone()
-                })
+                let doctype: JS<DocumentType> = DocumentTypeCast::to(abstract_self);
+                doctype.get().name.clone()
             },
             DocumentFragmentNodeTypeId => ~"#document-fragment",
-            DocumentNodeTypeId(_) => ~"#document"
+            DocumentNodeTypeId => ~"#document"
         }
     }
 
@@ -1004,7 +839,7 @@ impl Node {
     }
 
     // http://dom.spec.whatwg.org/#dom-node-ownerdocument
-    pub fn GetOwnerDocument(&self) -> Option<AbstractDocument> {
+    pub fn GetOwnerDocument(&self) -> Option<JS<Document>> {
         match self.type_id {
             ElementNodeTypeId(..) |
             CommentNodeTypeId |
@@ -1012,18 +847,20 @@ impl Node {
             ProcessingInstructionNodeTypeId |
             DoctypeNodeTypeId |
             DocumentFragmentNodeTypeId => Some(self.owner_doc()),
-            DocumentNodeTypeId(_) => None
+            DocumentNodeTypeId => None
         }
     }
 
     // http://dom.spec.whatwg.org/#dom-node-parentnode
-    pub fn GetParentNode(&self) -> Option<AbstractNode> {
-        self.parent_node
+    pub fn GetParentNode(&self) -> Option<JS<Node>> {
+        self.parent_node.clone()
     }
 
     // http://dom.spec.whatwg.org/#dom-node-parentelement
-    pub fn GetParentElement(&self) -> Option<AbstractNode> {
-        self.parent_node.filtered(|parent| parent.is_element())
+    pub fn GetParentElement(&self) -> Option<JS<Element>> {
+        self.parent_node.clone()
+                        .filtered(|parent| parent.is_element())
+                        .map(|node| ElementCast::to(&node))
     }
 
     // http://dom.spec.whatwg.org/#dom-node-haschildnodes
@@ -1032,34 +869,33 @@ impl Node {
     }
 
     // http://dom.spec.whatwg.org/#dom-node-firstchild
-    pub fn GetFirstChild(&self) -> Option<AbstractNode> {
-        self.first_child
+    pub fn GetFirstChild(&self) -> Option<JS<Node>> {
+        self.first_child.clone()
     }
 
     // http://dom.spec.whatwg.org/#dom-node-lastchild
-    pub fn GetLastChild(&self) -> Option<AbstractNode> {
-        self.last_child
+    pub fn GetLastChild(&self) -> Option<JS<Node>> {
+        self.last_child.clone()
     }
 
     // http://dom.spec.whatwg.org/#dom-node-previoussibling
-    pub fn GetPreviousSibling(&self) -> Option<AbstractNode> {
-        self.prev_sibling
+    pub fn GetPreviousSibling(&self) -> Option<JS<Node>> {
+        self.prev_sibling.clone()
     }
 
     // http://dom.spec.whatwg.org/#dom-node-nextsibling
-    pub fn GetNextSibling(&self) -> Option<AbstractNode> {
-        self.next_sibling
+    pub fn GetNextSibling(&self) -> Option<JS<Node>> {
+        self.next_sibling.clone()
     }
 
     // http://dom.spec.whatwg.org/#dom-node-nodevalue
-    pub fn GetNodeValue(&self, abstract_self: AbstractNode) -> Option<DOMString> {
+    pub fn GetNodeValue(&self, abstract_self: &JS<Node>) -> Option<DOMString> {
         match self.type_id {
             CommentNodeTypeId |
             TextNodeTypeId |
             ProcessingInstructionNodeTypeId => {
-                abstract_self.with_imm_characterdata(|characterdata| {
-                    Some(characterdata.Data())
-                })
+                let chardata: JS<CharacterData> = CharacterDataCast::to(abstract_self);
+                Some(chardata.get().Data())
             }
             _ => {
                 None
@@ -1068,23 +904,22 @@ impl Node {
     }
 
     // http://dom.spec.whatwg.org/#dom-node-nodevalue
-    pub fn SetNodeValue(&mut self, _abstract_self: AbstractNode, _val: Option<DOMString>)
+    pub fn SetNodeValue(&mut self, _abstract_self: &JS<Node>, _val: Option<DOMString>)
                         -> ErrorResult {
         // FIXME: Stub - https://github.com/mozilla/servo/issues/1655
         Ok(())
     }
 
     // http://dom.spec.whatwg.org/#dom-node-textcontent
-    pub fn GetTextContent(&self, abstract_self: AbstractNode) -> Option<DOMString> {
+    pub fn GetTextContent(&self, abstract_self: &JS<Node>) -> Option<DOMString> {
         match self.type_id {
             DocumentFragmentNodeTypeId |
             ElementNodeTypeId(..) => {
                 let mut content = ~"";
                 for node in abstract_self.traverse_preorder() {
                     if node.is_text() {
-                        node.with_imm_text(|text| {
-                            content.push_str(text.characterdata.data.as_slice());
-                        })
+                        let text: JS<Text> = TextCast::to(&node);
+                        content.push_str(text.get().characterdata.data.as_slice());
                     }
                 }
                 Some(content)
@@ -1092,42 +927,42 @@ impl Node {
             CommentNodeTypeId |
             TextNodeTypeId |
             ProcessingInstructionNodeTypeId => {
-                abstract_self.with_imm_characterdata(|characterdata| {
-                    Some(characterdata.Data())
-                })
+                let characterdata: JS<CharacterData> = CharacterDataCast::to(abstract_self);
+                Some(characterdata.get().Data())
             }
             DoctypeNodeTypeId |
-            DocumentNodeTypeId(_) => {
+            DocumentNodeTypeId => {
                 None
             }
         }
     }
 
     // http://dom.spec.whatwg.org/#dom-node-childnodes
-    pub fn ChildNodes(&mut self, abstract_self: AbstractNode) -> @mut NodeList {
+    pub fn ChildNodes(&mut self, abstract_self: &JS<Node>) -> JS<NodeList> {
         match self.child_list {
             None => {
-                let window = self.owner_doc().document().window;
-                let list = NodeList::new_child_list(window, abstract_self);
-                self.child_list = Some(list);
+                let doc = self.owner_doc();
+                let doc = doc.get();
+                let list = NodeList::new_child_list(&doc.window, abstract_self);
+                self.child_list = Some(list.clone());
                 list
             }
-            Some(list) => list
+            Some(ref list) => list.clone()
         }
     }
 
     // http://dom.spec.whatwg.org/#concept-node-adopt
-    fn adopt(node: AbstractNode, document: AbstractDocument) {
+    fn adopt(node: &mut JS<Node>, document: &JS<Document>) {
         // Step 1.
         match node.parent_node() {
-            Some(parent) => Node::remove(node, parent, Unsuppressed),
+            Some(ref mut parent) => Node::remove(node, parent, Unsuppressed),
             None => (),
         }
 
         // Step 2.
-        if node.node().owner_doc() != document {
-            for descendant in node.traverse_preorder() {
-                descendant.mut_node().set_owner_doc(document);
+        if node.get().owner_doc() != *document {
+            for mut descendant in node.traverse_preorder() {
+                descendant.get_mut().set_owner_doc(document);
             }
         }
 
@@ -1136,11 +971,11 @@ impl Node {
     }
 
     // http://dom.spec.whatwg.org/#concept-node-pre-insert
-    fn pre_insert(node: AbstractNode, parent: AbstractNode, child: Option<AbstractNode>)
-                  -> Fallible<AbstractNode> {
+    fn pre_insert(node: &mut JS<Node>, parent: &mut JS<Node>, child: Option<JS<Node>>)
+                  -> Fallible<JS<Node>> {
         // Step 1.
         match parent.type_id() {
-            DocumentNodeTypeId(..) |
+            DocumentNodeTypeId |
             DocumentFragmentNodeTypeId |
             ElementNodeTypeId(..) => (),
             _ => return Err(HierarchyRequest)
@@ -1153,7 +988,7 @@ impl Node {
 
         // Step 3.
         match child {
-            Some(child) if !parent.is_parent_of(child) => return Err(NotFound),
+            Some(ref child) if !parent.is_parent_of(child) => return Err(NotFound),
             _ => ()
         }
 
@@ -1161,13 +996,13 @@ impl Node {
         match node.type_id() {
             TextNodeTypeId => {
                 match node.parent_node() {
-                    Some(parent) if parent.is_document() => return Err(HierarchyRequest),
+                    Some(ref parent) if parent.is_document() => return Err(HierarchyRequest),
                     _ => ()
                 }
             }
             DoctypeNodeTypeId => {
                 match node.parent_node() {
-                    Some(parent) if !parent.is_document() => return Err(HierarchyRequest),
+                    Some(ref parent) if !parent.is_document() => return Err(HierarchyRequest),
                     _ => ()
                 }
             }
@@ -1175,12 +1010,12 @@ impl Node {
             ElementNodeTypeId(_) |
             ProcessingInstructionNodeTypeId |
             CommentNodeTypeId => (),
-            DocumentNodeTypeId(..) => return Err(HierarchyRequest)
+            DocumentNodeTypeId => return Err(HierarchyRequest)
         }
 
         // Step 6.
         match parent.type_id() {
-            DocumentNodeTypeId(_) => {
+            DocumentNodeTypeId => {
                 match node.type_id() {
                     // Step 6.1
                     DocumentFragmentNodeTypeId => {
@@ -1198,8 +1033,8 @@ impl Node {
                                     return Err(HierarchyRequest);
                                 }
                                 match child {
-                                    Some(child) if child.inclusively_following_siblings()
-                                                        .any(|child| child.is_doctype()) => {
+                                    Some(ref child) if child.inclusively_following_siblings()
+                                                            .any(|child| child.is_doctype()) => {
                                         return Err(HierarchyRequest);
                                     }
                                     _ => (),
@@ -1217,8 +1052,8 @@ impl Node {
                             return Err(HierarchyRequest);
                         }
                         match child {
-                            Some(child) if child.inclusively_following_siblings()
-                                                .any(|child| child.is_doctype()) => {
+                            Some(ref child) if child.inclusively_following_siblings()
+                                                    .any(|child| child.is_doctype()) => {
                                 return Err(HierarchyRequest);
                             }
                             _ => (),
@@ -1230,9 +1065,9 @@ impl Node {
                             return Err(HierarchyRequest);
                         }
                         match child {
-                            Some(child) => {
+                            Some(ref child) => {
                                 if parent.children()
-                                    .take_while(|&c| c != child)
+                                    .take_while(|c| c != child)
                                     .any(|c| c.is_element()) {
                                     return Err(HierarchyRequest);
                                 }
@@ -1249,48 +1084,47 @@ impl Node {
                     TextNodeTypeId |
                     ProcessingInstructionNodeTypeId |
                     CommentNodeTypeId => (),
-                    DocumentNodeTypeId(_) => unreachable!(),
+                    DocumentNodeTypeId => unreachable!(),
                 }
             },
             _ => (),
         }
 
         // Step 7-8.
-        let referenceChild = if child != Some(node) {
-            child
-        } else {
-            node.next_sibling()
+        let referenceChild = match child {
+            Some(ref child) if child == node => node.next_sibling(),
+            _ => child
         };
 
         // Step 9.
-        Node::adopt(node, parent.node().owner_doc());
+        Node::adopt(node, &parent.get().owner_doc());
 
         // Step 10.
         Node::insert(node, parent, referenceChild, Unsuppressed);
 
         // Step 11.
-        return Ok(node)
+        return Ok(node.clone())
     }
 
     // http://dom.spec.whatwg.org/#concept-node-insert
-    fn insert(node: AbstractNode,
-              parent: AbstractNode,
-              child: Option<AbstractNode>,
+    fn insert(node: &mut JS<Node>,
+              parent: &mut JS<Node>,
+              child: Option<JS<Node>>,
               suppress_observers: SuppressObserver) {
         // XXX assert owner_doc
         // Step 1-3: ranges.
         // Step 4.
-        let nodes = match node.type_id() {
+        let mut nodes = match node.type_id() {
             DocumentFragmentNodeTypeId => node.children().collect(),
-            _ => ~[node],
+            _ => ~[node.clone()],
         };
 
         // Step 5: DocumentFragment, mutation records.
         // Step 6: DocumentFragment.
         match node.type_id() {
             DocumentFragmentNodeTypeId => {
-                for c in node.children() {
-                    Node::remove(c, node, Suppressed);
+                for mut c in node.children() {
+                    Node::remove(&mut c, node, Suppressed);
                 }
             },
             _ => (),
@@ -1298,9 +1132,9 @@ impl Node {
 
         // Step 7: mutation records.
         // Step 8.
-        for node in nodes.iter() {
-            parent.add_child(*node, child);
-            node.mut_node().flags.set_is_in_doc(parent.is_in_doc());
+        for node in nodes.mut_iter() {
+            parent.add_child(node, child.clone());
+            node.get_mut().flags.set_is_in_doc(parent.is_in_doc());
         }
 
         // Step 9.
@@ -1315,33 +1149,33 @@ impl Node {
     }
 
     // http://dom.spec.whatwg.org/#concept-node-replace-all
-    pub fn replace_all(node: Option<AbstractNode>, parent: AbstractNode) {
+    pub fn replace_all(mut node: Option<JS<Node>>, parent: &mut JS<Node>) {
         // Step 1.
         match node {
-            Some(node) => Node::adopt(node, parent.node().owner_doc()),
+            Some(ref mut node) => Node::adopt(node, &parent.get().owner_doc()),
             None => (),
         }
 
         // Step 2.
-        let removedNodes: ~[AbstractNode] = parent.children().collect();
+        let removedNodes: ~[JS<Node>] = parent.children().collect();
 
         // Step 3.
         let addedNodes = match node {
             None => ~[],
-            Some(node) => match node.type_id() {
+            Some(ref node) => match node.type_id() {
                 DocumentFragmentNodeTypeId => node.children().collect(),
-                _ => ~[node],
+                _ => ~[node.clone()],
             },
         };
 
         // Step 4.
-        for child in parent.children() {
-            Node::remove(child, parent, Suppressed);
+        for mut child in parent.children() {
+            Node::remove(&mut child, parent, Suppressed);
         }
 
         // Step 5.
         match node {
-            Some(node) => Node::insert(node, parent, None, Suppressed),
+            Some(ref mut node) => Node::insert(node, parent, None, Suppressed),
             None => (),
         }
 
@@ -1357,28 +1191,29 @@ impl Node {
     }
 
     // http://dom.spec.whatwg.org/#concept-node-pre-remove
-    fn pre_remove(child: AbstractNode, parent: AbstractNode) -> Fallible<AbstractNode> {
+    fn pre_remove(child: &mut JS<Node>, parent: &mut JS<Node>) -> Fallible<JS<Node>> {
         // Step 1.
-        if child.parent_node() != Some(parent) {
-            return Err(NotFound);
+        match child.parent_node() {
+            Some(ref node) if node != parent => return Err(NotFound),
+            _ => ()
         }
 
         // Step 2.
         Node::remove(child, parent, Unsuppressed);
 
         // Step 3.
-        Ok(child)
+        Ok(child.clone())
     }
 
     // http://dom.spec.whatwg.org/#concept-node-remove
-    fn remove(node: AbstractNode, parent: AbstractNode, suppress_observers: SuppressObserver) {
-        assert!(node.parent_node() == Some(parent));
+    fn remove(node: &mut JS<Node>, parent: &mut JS<Node>, suppress_observers: SuppressObserver) {
+        assert!(node.parent_node().map_default(false, |ref node_parent| node_parent == parent));
 
         // Step 1-5: ranges.
         // Step 6-7: mutation observers.
         // Step 8.
         parent.remove_child(node);
-        node.mut_node().flags.set_is_in_doc(false);
+        node.get_mut().flags.set_is_in_doc(false);
 
         // Step 9.
         match suppress_observers {
@@ -1388,7 +1223,7 @@ impl Node {
     }
 
     // http://dom.spec.whatwg.org/#dom-node-textcontent
-    pub fn SetTextContent(&mut self, abstract_self: AbstractNode, value: Option<DOMString>)
+    pub fn SetTextContent(&mut self, abstract_self: &mut JS<Node>, value: Option<DOMString>)
                           -> ErrorResult {
         let value = null_str_as_empty(&value);
         match self.type_id {
@@ -1399,7 +1234,7 @@ impl Node {
                     None
                 } else {
                     let document = self.owner_doc();
-                    Some(document.document().CreateTextNode(document, value))
+                    Some(NodeCast::from(&document.get().CreateTextNode(&document, value)))
                 };
                 // Step 3.
                 Node::replace_all(node, abstract_self);
@@ -1409,43 +1244,42 @@ impl Node {
             ProcessingInstructionNodeTypeId => {
                 self.wait_until_safe_to_modify_dom();
 
-                abstract_self.with_mut_characterdata(|characterdata| {
-                    characterdata.data = value.clone();
+                let mut characterdata: JS<CharacterData> = CharacterDataCast::to(abstract_self);
+                characterdata.get_mut().data = value.clone();
 
-                    // Notify the document that the content of this node is different
-                    let document = self.owner_doc();
-                    document.document().content_changed();
-                })
+                // Notify the document that the content of this node is different
+                let document = self.owner_doc();
+                document.get().content_changed();
             }
             DoctypeNodeTypeId |
-            DocumentNodeTypeId(_) => {}
+            DocumentNodeTypeId => {}
         }
         Ok(())
     }
 
     // http://dom.spec.whatwg.org/#dom-node-insertbefore
-    pub fn InsertBefore(&self, abstract_self: AbstractNode, node: AbstractNode, child: Option<AbstractNode>)
-                        -> Fallible<AbstractNode> {
+    pub fn InsertBefore(&self, abstract_self: &mut JS<Node>, node: &mut JS<Node>, child: Option<JS<Node>>)
+                        -> Fallible<JS<Node>> {
         Node::pre_insert(node, abstract_self, child)
     }
 
     pub fn wait_until_safe_to_modify_dom(&self) {
         let document = self.owner_doc();
-        document.document().wait_until_safe_to_modify_dom();
+        document.get().wait_until_safe_to_modify_dom();
     }
 
     // http://dom.spec.whatwg.org/#dom-node-appendchild
-    pub fn AppendChild(&self, abstract_self: AbstractNode, node: AbstractNode)
-                       -> Fallible<AbstractNode> {
+    pub fn AppendChild(&self, abstract_self: &mut JS<Node>, node: &mut JS<Node>)
+                       -> Fallible<JS<Node>> {
         Node::pre_insert(node, abstract_self, None)
     }
 
     // http://dom.spec.whatwg.org/#concept-node-replace
-    pub fn ReplaceChild(&self, parent: AbstractNode, node: AbstractNode, child: AbstractNode)
-                        -> Fallible<AbstractNode> {
+    pub fn ReplaceChild(&self, parent: &mut JS<Node>, node: &mut JS<Node>, child: &mut JS<Node>)
+                        -> Fallible<JS<Node>> {
         // Step 1.
         match parent.type_id() {
-            DocumentNodeTypeId(..) |
+            DocumentNodeTypeId |
             DocumentFragmentNodeTypeId |
             ElementNodeTypeId(..) => (),
             _ => return Err(HierarchyRequest)
@@ -1471,12 +1305,12 @@ impl Node {
             TextNodeTypeId |
             ProcessingInstructionNodeTypeId |
             CommentNodeTypeId => (),
-            DocumentNodeTypeId(..) => return Err(HierarchyRequest)
+            DocumentNodeTypeId => return Err(HierarchyRequest)
         }
 
         // Step 6.
         match parent.type_id() {
-            DocumentNodeTypeId(..) => {
+            DocumentNodeTypeId => {
                 match node.type_id() {
                     // Step 6.1
                     DocumentFragmentNodeTypeId => {
@@ -1488,7 +1322,7 @@ impl Node {
                             0 => (),
                             // Step 6.1.2
                             1 => {
-                                if parent.child_elements().any(|c| c != child) {
+                                if parent.child_elements().any(|c| &NodeCast::from(&c) != child) {
                                     return Err(HierarchyRequest);
                                 }
                                 if child.following_siblings()
@@ -1502,7 +1336,7 @@ impl Node {
                     },
                     // Step 6.2
                     ElementNodeTypeId(..) => {
-                        if parent.child_elements().any(|c| c != child) {
+                        if parent.child_elements().any(|c| &NodeCast::from(&c) != child) {
                             return Err(HierarchyRequest);
                         }
                         if child.following_siblings()
@@ -1512,11 +1346,11 @@ impl Node {
                     },
                     // Step 6.3
                     DoctypeNodeTypeId => {
-                        if parent.children().any(|c| c.is_doctype() && c != child) {
+                        if parent.children().any(|c| c.is_doctype() && &c != child) {
                             return Err(HierarchyRequest);
                         }
                         if parent.children()
-                            .take_while(|&c| c != child)
+                            .take_while(|c| c != child)
                             .any(|c| c.is_element()) {
                             return Err(HierarchyRequest);
                         }
@@ -1524,26 +1358,26 @@ impl Node {
                     TextNodeTypeId |
                     ProcessingInstructionNodeTypeId |
                     CommentNodeTypeId => (),
-                    DocumentNodeTypeId(..) => unreachable!()
+                    DocumentNodeTypeId => unreachable!()
                 }
             },
             _ => ()
         }
 
         // Ok if not caught by previous error checks.
-        if node == child {
-            return Ok(child);
+        if *node == *child {
+            return Ok(child.clone());
         }
 
         // Step 7-8.
-        let reference_child = if child.next_sibling() != Some(node) {
-            child.next_sibling()
-        } else {
-            node.next_sibling()
+        let next_sibling = child.next_sibling();
+        let reference_child = match next_sibling {
+            Some(ref sibling) if sibling == node => node.next_sibling(),
+            _ => next_sibling
         };
 
         // Step 9.
-        Node::adopt(node, parent.node().owner_doc());
+        Node::adopt(node, &parent.get().owner_doc());
 
         {
             // Step 10.
@@ -1565,12 +1399,12 @@ impl Node {
         }
 
         // Step 15.
-        Ok(child)
+        Ok(child.clone())
     }
 
     // http://dom.spec.whatwg.org/#dom-node-removechild
-    pub fn RemoveChild(&self, abstract_self: AbstractNode, node: AbstractNode)
-                       -> Fallible<AbstractNode> {
+    pub fn RemoveChild(&self, abstract_self: &mut JS<Node>, node: &mut JS<Node>)
+                       -> Fallible<JS<Node>> {
         Node::pre_remove(node, abstract_self)
     }
 
@@ -1580,62 +1414,52 @@ impl Node {
     }
 
     // http://dom.spec.whatwg.org/#dom-node-clonenode
-    pub fn CloneNode(&self, _deep: bool) -> Fallible<AbstractNode> {
+    pub fn CloneNode(&self, _deep: bool) -> Fallible<JS<Node>> {
         // FIXME: stub - https://github.com/mozilla/servo/issues/1240
         fail!("stub")
     }
 
     // http://dom.spec.whatwg.org/#dom-node-isequalnode
-    pub fn IsEqualNode(&self, abstract_self: AbstractNode, maybe_node: Option<AbstractNode>) -> bool {
-        fn is_equal_doctype(node: AbstractNode, other: AbstractNode) -> bool {
-            node.with_imm_doctype(|doctype| {
-                other.with_imm_doctype(|other_doctype| {
-                    (doctype.name == other_doctype.name) &&
-                    (doctype.public_id == other_doctype.public_id) &&
-                    (doctype.system_id == other_doctype.system_id)
-                })
-            })
-        }
-        fn is_equal_element(node: AbstractNode, other: AbstractNode) -> bool {
-            node.with_imm_element(|element| {
-                other.with_imm_element(|other_element| {
-                    // FIXME: namespace prefix
-                    (element.namespace == other_element.namespace) &&
-                    (element.tag_name == other_element.tag_name) &&
-                    (element.attrs.len() == other_element.attrs.len())
-                })
-            })
-        }
-        fn is_equal_processinginstruction(node: AbstractNode, other: AbstractNode) -> bool {
-            node.with_imm_processing_instruction(|pi| {
-                other.with_imm_processing_instruction(|other_pi| {
-                    (pi.target == other_pi.target) &&
-                    (pi.characterdata.data == other_pi.characterdata.data)
-                })
-            })
-        }
-        fn is_equal_characterdata(node: AbstractNode, other: AbstractNode) -> bool {
-            node.with_imm_characterdata(|characterdata| {
-                other.with_imm_characterdata(|other_characterdata| {
-                    characterdata.data == other_characterdata.data
-                })
-            })
-        }
-        fn is_equal_element_attrs(node: AbstractNode, other: AbstractNode) -> bool {
-            node.with_imm_element(|element| {
-                other.with_imm_element(|other_element| {
-                    assert!(element.attrs.len() == other_element.attrs.len());
-                    element.attrs.iter().all(|attr| {
-                        other_element.attrs.iter().any(|other_attr| {
-                            (attr.namespace == other_attr.namespace) &&
-                            (attr.local_name == other_attr.local_name) &&
-                            (attr.value == other_attr.value)
-                        })
-                    })
+    pub fn IsEqualNode(&self, abstract_self: &JS<Node>, maybe_node: Option<JS<Node>>) -> bool {
+        fn is_equal_doctype(node: &JS<Node>, other: &JS<Node>) -> bool {
+            let doctype: JS<DocumentType> = DocumentTypeCast::to(node);
+            let other_doctype: JS<DocumentType> = DocumentTypeCast::to(other);
+            (doctype.get().name == other_doctype.get().name) &&
+            (doctype.get().public_id == other_doctype.get().public_id) &&
+            (doctype.get().system_id == other_doctype.get().system_id)
+        }
+        fn is_equal_element(node: &JS<Node>, other: &JS<Node>) -> bool {
+            let element: JS<Element> = ElementCast::to(node);
+            let other_element: JS<Element> = ElementCast::to(other);
+            // FIXME: namespace prefix
+            (element.get().namespace == other_element.get().namespace) &&
+            (element.get().tag_name == other_element.get().tag_name) &&
+            (element.get().attrs.len() == other_element.get().attrs.len())
+        }
+        fn is_equal_processinginstruction(node: &JS<Node>, other: &JS<Node>) -> bool {
+            let pi: JS<ProcessingInstruction> = ProcessingInstructionCast::to(node);
+            let other_pi: JS<ProcessingInstruction> = ProcessingInstructionCast::to(other);
+            (pi.get().target == other_pi.get().target) &&
+            (pi.get().characterdata.data == other_pi.get().characterdata.data)
+        }
+        fn is_equal_characterdata(node: &JS<Node>, other: &JS<Node>) -> bool {
+            let characterdata: JS<CharacterData> = CharacterDataCast::to(node);
+            let other_characterdata: JS<CharacterData> = CharacterDataCast::to(other);
+            characterdata.get().data == other_characterdata.get().data
+        }
+        fn is_equal_element_attrs(node: &JS<Node>, other: &JS<Node>) -> bool {
+            let element: JS<Element> = ElementCast::to(node);
+            let other_element: JS<Element> = ElementCast::to(other);
+            assert!(element.get().attrs.len() == other_element.get().attrs.len());
+            element.get().attrs.iter().all(|attr| {
+                other_element.get().attrs.iter().any(|other_attr| {
+                    (attr.get().namespace == other_attr.get().namespace) &&
+                    (attr.get().local_name == other_attr.get().local_name) &&
+                    (attr.get().value == other_attr.get().value)
                 })
             })
         }
-        fn is_equal_node(this: AbstractNode, node: AbstractNode) -> bool {
+        fn is_equal_node(this: &JS<Node>, node: &JS<Node>) -> bool {
             // Step 2.
             if this.type_id() != node.type_id() {
                 return false;
@@ -1659,27 +1483,27 @@ impl Node {
             }
 
             // Step 6.
-            this.children().zip(node.children()).all(|(child, other_child)| is_equal_node(child, other_child))
+            this.children().zip(node.children()).all(|(ref child, ref other_child)| is_equal_node(child, other_child))
         }
         match maybe_node {
             // Step 1.
             None => false,
             // Step 2-6.
-            Some(node) => is_equal_node(abstract_self, node)
+            Some(ref node) => is_equal_node(abstract_self, node)
         }
     }
 
     // http://dom.spec.whatwg.org/#dom-node-comparedocumentposition
-    pub fn CompareDocumentPosition(&self, _other: AbstractNode) -> u16 {
+    pub fn CompareDocumentPosition(&self, _other: &JS<Node>) -> u16 {
         // FIXME: stub - https://github.com/mozilla/servo/issues/1655
         0
     }
 
     // http://dom.spec.whatwg.org/#dom-node-contains
-    pub fn Contains(&self, abstract_self: AbstractNode, maybe_other: Option<AbstractNode>) -> bool {
+    pub fn Contains(&self, abstract_self: &JS<Node>, maybe_other: Option<JS<Node>>) -> bool {
         match maybe_other {
             None => false,
-            Some(other) => abstract_self.is_inclusive_ancestor_of(other)
+            Some(ref other) => abstract_self.is_inclusive_ancestor_of(other)
         }
     }
 
@@ -1725,33 +1549,33 @@ impl Node {
     // Low-level pointer stitching
     //
 
-    pub fn set_parent_node(&mut self, new_parent_node: Option<AbstractNode>) {
+    pub fn set_parent_node(&mut self, new_parent_node: Option<JS<Node>>) {
         let doc = self.owner_doc();
-        doc.document().wait_until_safe_to_modify_dom();
+        doc.get().wait_until_safe_to_modify_dom();
         self.parent_node = new_parent_node
     }
 
-    pub fn set_first_child(&mut self, new_first_child: Option<AbstractNode>) {
+    pub fn set_first_child(&mut self, new_first_child: Option<JS<Node>>) {
         let doc = self.owner_doc();
-        doc.document().wait_until_safe_to_modify_dom();
+        doc.get().wait_until_safe_to_modify_dom();
         self.first_child = new_first_child
     }
 
-    pub fn set_last_child(&mut self, new_last_child: Option<AbstractNode>) {
+    pub fn set_last_child(&mut self, new_last_child: Option<JS<Node>>) {
         let doc = self.owner_doc();
-        doc.document().wait_until_safe_to_modify_dom();
+        doc.get().wait_until_safe_to_modify_dom();
         self.last_child = new_last_child
     }
 
-    pub fn set_prev_sibling(&mut self, new_prev_sibling: Option<AbstractNode>) {
+    pub fn set_prev_sibling(&mut self, new_prev_sibling: Option<JS<Node>>) {
         let doc = self.owner_doc();
-        doc.document().wait_until_safe_to_modify_dom();
+        doc.get().wait_until_safe_to_modify_dom();
         self.prev_sibling = new_prev_sibling
     }
 
-    pub fn set_next_sibling(&mut self, new_next_sibling: Option<AbstractNode>) {
+    pub fn set_next_sibling(&mut self, new_next_sibling: Option<JS<Node>>) {
         let doc = self.owner_doc();
-        doc.document().wait_until_safe_to_modify_dom();
+        doc.get().wait_until_safe_to_modify_dom();
         self.next_sibling = new_next_sibling
     }
 
diff --git a/src/components/script/dom/nodelist.rs b/src/components/script/dom/nodelist.rs
index 6857add6600..84de1a56d19 100644
--- a/src/components/script/dom/nodelist.rs
+++ b/src/components/script/dom/nodelist.rs
@@ -3,43 +3,46 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::NodeListBinding;
+use dom::bindings::js::JS;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
-use dom::node::AbstractNode;
+use dom::node::{Node, NodeHelpers};
 use dom::window::Window;
 
+#[deriving(Encodable)]
 enum NodeListType {
-    Simple(~[AbstractNode]),
-    Children(AbstractNode)
+    Simple(~[JS<Node>]),
+    Children(JS<Node>)
 }
 
+#[deriving(Encodable)]
 pub struct NodeList {
     list_type: NodeListType,
     reflector_: Reflector,
-    window: @mut Window,
+    window: JS<Window>
 }
 
 impl NodeList {
-    pub fn new_inherited(window: @mut Window,
+    pub fn new_inherited(window: JS<Window>,
                          list_type: NodeListType) -> NodeList {
         NodeList {
             list_type: list_type,
             reflector_: Reflector::new(),
-            window: window,
+            window: window
         }
     }
 
-    pub fn new(window: @mut Window,
-               list_type: NodeListType) -> @mut NodeList {
-        reflect_dom_object(@mut NodeList::new_inherited(window, list_type),
-                           window, NodeListBinding::Wrap)
+    pub fn new(window: JS<Window>,
+               list_type: NodeListType) -> JS<NodeList> {
+        reflect_dom_object(~NodeList::new_inherited(window.clone(), list_type),
+                           window.get(), NodeListBinding::Wrap)
     }
 
-    pub fn new_simple_list(window: @mut Window, elements: ~[AbstractNode]) -> @mut NodeList {
-        NodeList::new(window, Simple(elements))
+    pub fn new_simple_list(window: &JS<Window>, elements: ~[JS<Node>]) -> JS<NodeList> {
+        NodeList::new(window.clone(), Simple(elements))
     }
 
-    pub fn new_child_list(window: @mut Window, node: AbstractNode) -> @mut NodeList {
-        NodeList::new(window, Children(node))
+    pub fn new_child_list(window: &JS<Window>, node: &JS<Node>) -> JS<NodeList> {
+        NodeList::new(window.clone(), Children(node.clone()))
     }
 
     pub fn Length(&self) -> u32 {
@@ -49,15 +52,15 @@ impl NodeList {
         }
     }
 
-    pub fn Item(&self, index: u32) -> Option<AbstractNode> {
+    pub fn Item(&self, index: u32) -> Option<JS<Node>> {
         match self.list_type {
             _ if index >= self.Length() => None,
-            Simple(ref elems) => Some(elems[index]),
+            Simple(ref elems) => Some(elems[index].clone()),
             Children(ref node) => node.children().nth(index as uint)
         }
     }
 
-    pub fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<AbstractNode> {
+    pub fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<JS<Node>> {
         let item = self.Item(index);
         *found = item.is_some();
         item
diff --git a/src/components/script/dom/processinginstruction.rs b/src/components/script/dom/processinginstruction.rs
index 0fd830be452..85d247fe94a 100644
--- a/src/components/script/dom/processinginstruction.rs
+++ b/src/components/script/dom/processinginstruction.rs
@@ -3,28 +3,41 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::ProcessingInstructionBinding;
+use dom::bindings::codegen::InheritTypes::ProcessingInstructionDerived;
+use dom::bindings::js::JS;
 use dom::characterdata::CharacterData;
-use dom::document::AbstractDocument;
-use dom::node::{AbstractNode, Node, ProcessingInstructionNodeTypeId};
+use dom::document::Document;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::node::{Node, ProcessingInstructionNodeTypeId};
 use servo_util::str::DOMString;
 
 /// An HTML processing instruction node.
+#[deriving(Encodable)]
 pub struct ProcessingInstruction {
     characterdata: CharacterData,
     target: DOMString,
 }
 
+impl ProcessingInstructionDerived for EventTarget {
+    fn is_processinginstruction(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(ProcessingInstructionNodeTypeId) => true,
+            _ => false
+        }
+    }
+}
+
 impl ProcessingInstruction {
-    pub fn new_inherited(target: DOMString, data: DOMString, document: AbstractDocument) -> ProcessingInstruction {
+    pub fn new_inherited(target: DOMString, data: DOMString, document: JS<Document>) -> ProcessingInstruction {
         ProcessingInstruction {
             characterdata: CharacterData::new_inherited(ProcessingInstructionNodeTypeId, data, document),
             target: target
         }
     }
 
-    pub fn new(target: DOMString, data: DOMString, document: AbstractDocument) -> AbstractNode {
-        let node = ProcessingInstruction::new_inherited(target, data, document);
-        Node::reflect_node(@mut node, document, ProcessingInstructionBinding::Wrap)
+    pub fn new(target: DOMString, data: DOMString, document: &JS<Document>) -> JS<ProcessingInstruction> {
+        let node = ProcessingInstruction::new_inherited(target, data, document.clone());
+        Node::reflect_node(~node, document, ProcessingInstructionBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/dom/text.rs b/src/components/script/dom/text.rs
index 9ed8ba7a8b6..2d81937849e 100644
--- a/src/components/script/dom/text.rs
+++ b/src/components/script/dom/text.rs
@@ -3,35 +3,48 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::TextBinding;
+use dom::bindings::codegen::InheritTypes::TextDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::Fallible;
 use dom::characterdata::CharacterData;
-use dom::document::AbstractDocument;
-use dom::node::{AbstractNode, Node, TextNodeTypeId};
+use dom::document::Document;
+use dom::eventtarget::{EventTarget, NodeTargetTypeId};
+use dom::node::{Node, TextNodeTypeId};
 use dom::window::Window;
 use servo_util::str::DOMString;
 
 /// An HTML text node.
+#[deriving(Encodable)]
 pub struct Text {
     characterdata: CharacterData,
 }
 
+impl TextDerived for EventTarget {
+    fn is_text(&self) -> bool {
+        match self.type_id {
+            NodeTargetTypeId(TextNodeTypeId) => true,
+            _ => false
+        }
+    }
+}
+
 impl Text {
-    pub fn new_inherited(text: DOMString, document: AbstractDocument) -> Text {
+    pub fn new_inherited(text: DOMString, document: JS<Document>) -> Text {
         Text {
             characterdata: CharacterData::new_inherited(TextNodeTypeId, text, document)
         }
     }
 
-    pub fn new(text: DOMString, document: AbstractDocument) -> AbstractNode {
-        let node = Text::new_inherited(text, document);
-        Node::reflect_node(@mut node, document, TextBinding::Wrap)
+    pub fn new(text: DOMString, document: &JS<Document>) -> JS<Text> {
+        let node = Text::new_inherited(text, document.clone());
+        Node::reflect_node(~node, document, TextBinding::Wrap)
     }
 
-    pub fn Constructor(owner: @mut Window, text: DOMString) -> Fallible<AbstractNode> {
-        Ok(Text::new(text.clone(), owner.Document()))
+    pub fn Constructor(owner: &JS<Window>, text: DOMString) -> Fallible<JS<Text>> {
+        Ok(Text::new(text.clone(), &owner.get().Document()))
     }
 
-    pub fn SplitText(&self, _offset: u32) -> Fallible<AbstractNode> {
+    pub fn SplitText(&self, _offset: u32) -> Fallible<JS<Text>> {
         fail!("unimplemented")
     }
 
diff --git a/src/components/script/dom/uievent.rs b/src/components/script/dom/uievent.rs
index 4ae1c6869b2..92e36edd6a5 100644
--- a/src/components/script/dom/uievent.rs
+++ b/src/components/script/dom/uievent.rs
@@ -3,47 +3,55 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::UIEventBinding;
+use dom::bindings::codegen::InheritTypes::UIEventDerived;
+use dom::bindings::js::JS;
 use dom::bindings::utils::Fallible;
 use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
-use dom::node::AbstractNode;
-use dom::event::{AbstractEvent, Event, EventTypeId, UIEventTypeId};
+use dom::event::{Event, EventTypeId, UIEventTypeId};
+use dom::node::Node;
 use dom::window::Window;
 use dom::windowproxy::WindowProxy;
 use servo_util::str::DOMString;
 
+#[deriving(Encodable)]
 pub struct UIEvent {
-    parent: Event,
-    view: Option<@mut WindowProxy>,
+    event: Event,
+    view: Option<JS<WindowProxy>>,
     detail: i32
 }
 
+impl UIEventDerived for Event {
+    fn is_uievent(&self) -> bool {
+        self.type_id == UIEventTypeId
+    }
+}
+
 impl UIEvent {
     pub fn new_inherited(type_id: EventTypeId) -> UIEvent {
         UIEvent {
-            parent: Event::new_inherited(type_id),
+            event: Event::new_inherited(type_id),
             view: None,
             detail: 0
         }
     }
 
-    pub fn new(window: @mut Window) -> AbstractEvent {
-        let ev = reflect_dom_object(@mut UIEvent::new_inherited(UIEventTypeId),
-                                    window,
-                                    UIEventBinding::Wrap);
-        Event::as_abstract(ev)
+    pub fn new(window: &JS<Window>) -> JS<UIEvent> {
+        reflect_dom_object(~UIEvent::new_inherited(UIEventTypeId),
+                           window.get(),
+                           UIEventBinding::Wrap)
     }
 
-    pub fn Constructor(owner: @mut Window,
+    pub fn Constructor(owner: &JS<Window>,
                        type_: DOMString,
-                       init: &UIEventBinding::UIEventInit) -> Fallible<AbstractEvent> {
-        let ev = UIEvent::new(owner);
-        ev.mut_uievent().InitUIEvent(type_, init.parent.bubbles, init.parent.cancelable,
-                                     init.view, init.detail);
+                       init: &UIEventBinding::UIEventInit) -> Fallible<JS<UIEvent>> {
+        let mut ev = UIEvent::new(owner);
+        ev.get_mut().InitUIEvent(type_, init.parent.bubbles, init.parent.cancelable,
+                                   init.view.clone(), init.detail);
         Ok(ev)
     }
 
-    pub fn GetView(&self) -> Option<@mut WindowProxy> {
-        self.view
+    pub fn GetView(&self) -> Option<JS<WindowProxy>> {
+        self.view.clone()
     }
 
     pub fn Detail(&self) -> i32 {
@@ -54,9 +62,9 @@ impl UIEvent {
                        type_: DOMString,
                        can_bubble: bool,
                        cancelable: bool,
-                       view: Option<@mut WindowProxy>,
+                       view: Option<JS<WindowProxy>>,
                        detail: i32) {
-        self.parent.InitEvent(type_, can_bubble, cancelable);
+        self.event.InitEvent(type_, can_bubble, cancelable);
         self.view = view;
         self.detail = detail;
     }
@@ -86,7 +94,7 @@ impl UIEvent {
         0
     }
 
-    pub fn GetRangeParent(&self) -> Option<AbstractNode> {
+    pub fn GetRangeParent(&self) -> Option<JS<Node>> {
         //TODO
         None
     }
@@ -113,10 +121,10 @@ impl UIEvent {
 
 impl Reflectable for UIEvent {
     fn reflector<'a>(&'a self) -> &'a Reflector {
-        self.parent.reflector()
+        self.event.reflector()
     }
 
     fn mut_reflector<'a>(&'a mut self) -> &'a mut Reflector {
-        self.parent.mut_reflector()
+        self.event.mut_reflector()
     }
 }
diff --git a/src/components/script/dom/validitystate.rs b/src/components/script/dom/validitystate.rs
index 562b58a16c6..1d7a690ffab 100644
--- a/src/components/script/dom/validitystate.rs
+++ b/src/components/script/dom/validitystate.rs
@@ -2,18 +2,20 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::codegen::ValidityStateBinding;
+use dom::bindings::js::JS;
+use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
 use dom::window::Window;
 
+#[deriving(Encodable)]
 pub struct ValidityState {
     reflector_: Reflector,
-    window: @mut Window,
+    window: JS<Window>,
     state: u8,
 }
 
 impl ValidityState {
-    pub fn new_inherited(window: @mut Window) -> ValidityState {
+    pub fn new_inherited(window: JS<Window>) -> ValidityState {
         ValidityState {
             reflector_: Reflector::new(),
             window: window,
@@ -21,8 +23,9 @@ impl ValidityState {
         }
     }
 
-    pub fn new(window: @mut Window) -> @mut ValidityState {
-        reflect_dom_object(@mut ValidityState::new_inherited(window), window,
+    pub fn new(window: &JS<Window>) -> JS<ValidityState> {
+        reflect_dom_object(~ValidityState::new_inherited(window.clone()),
+                           window.get(),
                            ValidityStateBinding::Wrap)
     }
 }
diff --git a/src/components/script/dom/webidls/Document.webidl b/src/components/script/dom/webidls/Document.webidl
index 12769016f38..daa91f540fb 100644
--- a/src/components/script/dom/webidls/Document.webidl
+++ b/src/components/script/dom/webidls/Document.webidl
@@ -21,8 +21,6 @@ interface Document : Node {
   readonly attribute DocumentType? doctype;
   readonly attribute Element? documentElement;
   HTMLCollection getElementsByTagName(DOMString localName);
-  HTMLCollection getElementsByTagNameNS(DOMString? namespace, DOMString localName);
-  HTMLCollection getElementsByClassName(DOMString classNames);
   Element? getElementById(DOMString elementId);
 
   [Creator, Throws]
@@ -47,4 +45,13 @@ partial interface Document {
            attribute HTMLElement? body;
   readonly attribute HTMLHeadElement? head;
   /*NodeList*/ HTMLCollection getElementsByName(DOMString elementName);
+
+  readonly attribute HTMLCollection images;
+  readonly attribute HTMLCollection embeds;
+  readonly attribute HTMLCollection plugins;
+  readonly attribute HTMLCollection links;
+  readonly attribute HTMLCollection forms;
+  readonly attribute HTMLCollection scripts;
+  readonly attribute HTMLCollection anchors;
+  readonly attribute HTMLCollection applets;
 };
diff --git a/src/components/script/dom/webidls/HTMLDocument.webidl b/src/components/script/dom/webidls/HTMLDocument.webidl
deleted file mode 100644
index b899a46678f..00000000000
--- a/src/components/script/dom/webidls/HTMLDocument.webidl
+++ /dev/null
@@ -1,17 +0,0 @@
-/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/.
- */
-
-/* http://www.whatwg.org/specs/web-apps/current-work/#the-document-object */
-interface HTMLDocument : Document {
-  readonly attribute HTMLCollection images;
-  readonly attribute HTMLCollection embeds;
-  readonly attribute HTMLCollection plugins;
-  readonly attribute HTMLCollection links;
-  readonly attribute HTMLCollection forms;
-  readonly attribute HTMLCollection scripts;
-  readonly attribute HTMLCollection anchors;
-  readonly attribute HTMLCollection applets;
-};
diff --git a/src/components/script/dom/webidls/HTMLSelectElement.webidl b/src/components/script/dom/webidls/HTMLSelectElement.webidl
index b99bf149280..bb843fd3f92 100644
--- a/src/components/script/dom/webidls/HTMLSelectElement.webidl
+++ b/src/components/script/dom/webidls/HTMLSelectElement.webidl
@@ -32,8 +32,8 @@ interface HTMLSelectElement : HTMLElement {
            attribute unsigned long length;
   getter Element? item(unsigned long index);
   HTMLOptionElement? namedItem(DOMString name);
-  /*[Throws]
-    void add((HTMLOptionElement or HTMLOptGroupElement) element, optional (HTMLElement or long)? before = null);*/
+  [Throws]
+    void add((HTMLOptionElement or HTMLOptGroupElement) element, optional (HTMLElement or long)? before = null);
   void remove(long index);
   [Throws]
   setter creator void (unsigned long index, HTMLOptionElement? option);
diff --git a/src/components/script/dom/window.rs b/src/components/script/dom/window.rs
index 3596c5de9f9..5c78af9f0d2 100644
--- a/src/components/script/dom/window.rs
+++ b/src/components/script/dom/window.rs
@@ -3,11 +3,11 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::codegen::WindowBinding;
-use dom::bindings::utils::{Reflectable, Reflector, Traceable};
-use dom::bindings::utils::{trace_option, trace_reflector};
-use dom::document::AbstractDocument;
+use dom::bindings::js::JS;
+use dom::bindings::utils::{Reflectable, Reflector};
+use dom::document::Document;
+use dom::element::Element;
 use dom::eventtarget::{EventTarget, WindowTypeId};
-use dom::node::AbstractNode;
 use dom::console::Console;
 use dom::location::Location;
 use dom::navigator::Navigator;
@@ -20,7 +20,7 @@ use servo_util::str::DOMString;
 use servo_util::task::{spawn_named};
 
 use js::glue::*;
-use js::jsapi::{JSObject, JSContext, JS_DefineProperty, JSTracer, JSVal};
+use js::jsapi::{JSObject, JSContext, JS_DefineProperty, JSVal};
 use js::{JSVAL_NULL, JSPROP_ENUMERATE};
 
 use std::cast;
@@ -32,6 +32,8 @@ use std::num;
 use std::ptr;
 use std::to_bytes::Cb;
 
+use extra::serialize::{Encoder, Encodable};
+
 pub enum TimerControlMsg {
     TimerMessage_Fire(~TimerData),
     TimerMessage_Close,
@@ -43,6 +45,11 @@ pub struct TimerHandle {
     cancel_chan: Option<Chan<()>>,
 }
 
+impl<S: Encoder> Encodable<S> for TimerHandle {
+    fn encode(&self, _: &mut S) {
+    }
+}
+
 impl IterBytes for TimerHandle {
     fn iter_bytes(&self, lsb0: bool, f: Cb) -> bool {
         self.handle.iter_bytes(lsb0, f)
@@ -61,18 +68,28 @@ impl TimerHandle {
     }
 }
 
+#[deriving(Encodable)]
 pub struct Window {
     eventtarget: EventTarget,
     page: @mut Page,
     script_chan: ScriptChan,
     compositor: @ScriptListener,
-    console: Option<@mut Console>,
-    timer_chan: SharedChan<TimerControlMsg>,
-    location: Option<@mut Location>,
-    navigator: Option<@mut Navigator>,
+    console: Option<JS<Console>>,
+    location: Option<JS<Location>>,
+    navigator: Option<JS<Navigator>>,
     image_cache_task: ImageCacheTask,
     active_timers: ~HashSet<TimerHandle>,
     next_timer_handle: i32,
+    extra: Untraceable
+}
+
+struct Untraceable {
+    timer_chan: SharedChan<TimerControlMsg>,
+}
+
+impl<S: Encoder> Encodable<S> for Untraceable {
+    fn encode(&self, _: &mut S) {
+    }
 }
 
 impl Window {
@@ -84,7 +101,7 @@ impl Window {
 #[unsafe_destructor]
 impl Drop for Window {
     fn drop(&mut self) {
-        self.timer_chan.send(TimerMessage_Close);
+        self.extra.timer_chan.send(TimerMessage_Close);
         for handle in self.active_timers.iter() {
             handle.cancel();
         }
@@ -107,11 +124,11 @@ impl Window {
     }
 
     pub fn Close(&self) {
-        self.timer_chan.send(TimerMessage_TriggerExit);
+        self.extra.timer_chan.send(TimerMessage_TriggerExit);
     }
 
-    pub fn Document(&self) -> AbstractDocument {
-        self.page.frame.unwrap().document
+    pub fn Document(&self) -> JS<Document> {
+        self.page.frame.get_ref().document.clone()
     }
 
     pub fn Name(&self) -> DOMString {
@@ -141,29 +158,29 @@ impl Window {
     pub fn Blur(&self) {
     }
 
-    pub fn GetFrameElement(&self) -> Option<AbstractNode> {
+    pub fn GetFrameElement(&self) -> Option<JS<Element>> {
         None
     }
 
-    pub fn Location(&mut self) -> @mut Location {
+    pub fn Location(&mut self) -> JS<Location> {
         if self.location.is_none() {
             self.location = Some(Location::new(self, self.page));
         }
-        self.location.unwrap()
+        self.location.get_ref().clone()
     }
 
-    pub fn Console(&mut self) -> @mut Console {
+    pub fn Console(&mut self) -> JS<Console> {
         if self.console.is_none() {
             self.console = Some(Console::new(self));
         }
-        self.console.unwrap()
+        self.console.get_ref().clone()
     }
 
-    pub fn Navigator(&mut self) -> @mut Navigator {
+    pub fn Navigator(&mut self) -> JS<Navigator> {
         if self.navigator.is_none() {
             self.navigator = Some(Navigator::new(self));
         }
-        self.navigator.unwrap()
+        self.navigator.get_ref().clone()
     }
 
     pub fn Confirm(&self, _message: DOMString) -> bool {
@@ -202,7 +219,7 @@ impl Window {
         // to the relevant script handler that will deal with it.
         let tm = Timer::new().unwrap();
         let (cancel_port, cancel_chan) = Chan::new();
-        let chan = self.timer_chan.clone();
+        let chan = self.extra.timer_chan.clone();
         spawn_named("Window:SetTimeout", proc() {
             let mut tm = tm;
             let mut timeout_port = tm.oneshot(timeout);
@@ -249,26 +266,28 @@ impl Window {
                script_chan: ScriptChan,
                compositor: @ScriptListener,
                image_cache_task: ImageCacheTask)
-               -> @mut Window {
-        let win = @mut Window {
+               -> JS<Window> {
+        let mut win = ~Window {
             eventtarget: EventTarget::new_inherited(WindowTypeId),
             page: page,
             script_chan: script_chan.clone(),
             compositor: compositor,
             console: None,
-            timer_chan: {
-                let (timer_port, timer_chan): (Port<TimerControlMsg>, SharedChan<TimerControlMsg>) = SharedChan::new();
-                let id = page.id.clone();
-                spawn_named("timer controller", proc() {
-                    loop {
-                        match timer_port.recv() {
-                            TimerMessage_Close => break,
-                            TimerMessage_Fire(td) => script_chan.send(FireTimerMsg(id, td)),
-                            TimerMessage_TriggerExit => script_chan.send(ExitWindowMsg(id)),
+            extra: Untraceable {
+                timer_chan: {
+                    let (timer_port, timer_chan): (Port<TimerControlMsg>, SharedChan<TimerControlMsg>) = SharedChan::new();
+                    let id = page.id.clone();
+                    spawn_named("timer controller", proc() {
+                        loop {
+                            match timer_port.recv() {
+                                TimerMessage_Close => break,
+                                TimerMessage_Fire(td) => script_chan.send(FireTimerMsg(id, td)),
+                                TimerMessage_TriggerExit => script_chan.send(ExitWindowMsg(id)),
+                            }
                         }
-                    }
-                });
-                timer_chan
+                    });
+                    timer_chan
+                }
             },
             location: None,
             navigator: None,
@@ -277,7 +296,9 @@ impl Window {
             next_timer_handle: 0
         };
 
+        let raw: *mut Window = &mut *win;
         let global = WindowBinding::Wrap(cx, ptr::null(), win);
+        assert!(global.is_not_null());
         unsafe {
             let fn_names = ["window","self"];
             for str in fn_names.iter() {
@@ -291,17 +312,7 @@ impl Window {
 
             }
 
+            JS::from_raw(raw)
         }
-        win
-    }
-}
-
-impl Traceable for Window {
-    fn trace(&self, tracer: *mut JSTracer) {
-        debug!("tracing window");
-
-        self.page.frame.map(|frame| trace_reflector(tracer, "document", frame.document.reflector()));
-        trace_option(tracer, "location", self.location);
-        trace_option(tracer, "navigator", self.navigator);
     }
 }
diff --git a/src/components/script/dom/windowproxy.rs b/src/components/script/dom/windowproxy.rs
index bae5c5b933f..35304d25d3c 100644
--- a/src/components/script/dom/windowproxy.rs
+++ b/src/components/script/dom/windowproxy.rs
@@ -2,17 +2,22 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use dom::bindings::utils::{Reflectable, Reflector};
+use dom::bindings::codegen::WindowProxyBinding;
+use dom::bindings::js::JS;
+use dom::bindings::utils::{Reflectable, Reflector, reflect_dom_object};
+use dom::window::Window;
 
+#[deriving(Encodable)]
 pub struct WindowProxy {
     reflector_: Reflector
 }
 
 impl WindowProxy {
-    pub fn new() -> @mut WindowProxy {
-        @mut WindowProxy {
+    pub fn new(owner: JS<Window>) -> JS<WindowProxy> {
+        let proxy = ~WindowProxy {
             reflector_: Reflector::new()
-        }
+        };
+        reflect_dom_object(proxy, owner.get(), WindowProxyBinding::Wrap)
     }
 }
 
diff --git a/src/components/script/html/hubbub_html_parser.rs b/src/components/script/html/hubbub_html_parser.rs
index d388a77b0e3..cf692d43dfd 100644
--- a/src/components/script/html/hubbub_html_parser.rs
+++ b/src/components/script/html/hubbub_html_parser.rs
@@ -2,13 +2,17 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::{NodeBase, NodeCast, TextCast, ElementCast};
+use dom::bindings::codegen::InheritTypes::{HTMLIFrameElementCast, HTMLImageElementCast};
+use dom::bindings::js::JS;
+use dom::bindings::utils::Reflectable;
+use dom::document::Document;
 use dom::element::{HTMLLinkElementTypeId, HTMLIframeElementTypeId, HTMLImageElementTypeId};
 use dom::htmlelement::HTMLElement;
 use dom::htmlheadingelement::{Heading1, Heading2, Heading3, Heading4, Heading5, Heading6};
 use dom::htmliframeelement::IFrameSize;
 use dom::htmlformelement::HTMLFormElement;
-use dom::node::{AbstractNode, ElementNodeTypeId};
+use dom::node::{ElementNodeTypeId, INode, NodeHelpers};
 use dom::types::*;
 use html::cssparse::{InlineProvenance, StylesheetProvenance, UrlProvenance, spawn_css_parser};
 use script_task::page_from_context;
@@ -36,7 +40,7 @@ macro_rules! handle_element(
      $ctor: ident
      $(, $arg:expr )*) => (
         if $string == $localName {
-            return $ctor::new($localName, $document $(, $arg)*);
+            return ElementCast::from(&$ctor::new($localName, $document $(, $arg)*));
         }
     )
 )
@@ -72,16 +76,16 @@ pub struct HtmlParserResult {
 }
 
 trait NodeWrapping {
-    unsafe fn to_hubbub_node(self) -> hubbub::NodeDataPtr;
+    unsafe fn to_hubbub_node(&self) -> hubbub::NodeDataPtr;
     unsafe fn from_hubbub_node(n: hubbub::NodeDataPtr) -> Self;
 }
 
-impl NodeWrapping for AbstractNode {
-    unsafe fn to_hubbub_node(self) -> hubbub::NodeDataPtr {
-        cast::transmute(self)
+impl<T: NodeBase+Reflectable> NodeWrapping for JS<T> {
+    unsafe fn to_hubbub_node(&self) -> hubbub::NodeDataPtr {
+        cast::transmute(self.get())
     }
-    unsafe fn from_hubbub_node(n: hubbub::NodeDataPtr) -> AbstractNode {
-        cast::transmute(n)
+    unsafe fn from_hubbub_node(n: hubbub::NodeDataPtr) -> JS<T> {
+        JS::from_raw(cast::transmute(n))
     }
 }
 
@@ -158,7 +162,7 @@ fn js_script_listener(to_parent: SharedChan<HtmlDiscoveryMessage>,
 // Silly macros to handle constructing      DOM nodes. This produces bad code and should be optimized
 // via atomization (issue #85).
 
-pub fn build_element_from_tag(tag: DOMString, document: AbstractDocument) -> AbstractNode {
+pub fn build_element_from_tag(tag: DOMString, document: &JS<Document>) -> JS<Element> {
     // TODO (Issue #85): use atoms
     handle_element!(document, tag, "a",         HTMLAnchorElement);
     handle_element!(document, tag, "applet",    HTMLAppletElement);
@@ -240,11 +244,11 @@ pub fn build_element_from_tag(tag: DOMString, document: AbstractDocument) -> Abs
     handle_element!(document, tag, "ul",        HTMLUListElement);
     handle_element!(document, tag, "video",     HTMLVideoElement);
 
-    return HTMLUnknownElement::new(tag, document);
+    return ElementCast::from(&HTMLUnknownElement::new(tag, document));
 }
 
 pub fn parse_html(cx: *JSContext,
-                  document: AbstractDocument,
+                  document: &mut JS<Document>,
                   url: Url,
                   resource_task: ResourceTask,
                   image_cache_task: ImageCacheTask,
@@ -294,8 +298,7 @@ pub fn parse_html(cx: *JSContext,
     let mut parser = hubbub::Parser("UTF-8", false);
     debug!("created parser");
 
-    let document_node = AbstractNode::from_document(document);
-    parser.set_document_node(unsafe { document_node.to_hubbub_node() });
+    parser.set_document_node(unsafe { document.to_hubbub_node() });
     parser.enable_scripting(true);
     parser.enable_styling(true);
 
@@ -306,7 +309,7 @@ pub fn parse_html(cx: *JSContext,
     let tree_handler = hubbub::TreeHandler {
         create_comment: |data: ~str| {
             debug!("create comment");
-            let comment = Comment::new(data, document);
+            let comment: JS<Node> = NodeCast::from(&Comment::new(data, document));
             unsafe { comment.to_hubbub_node() }
         },
         create_doctype: |doctype: ~hubbub::Doctype| {
@@ -315,87 +318,81 @@ pub fn parse_html(cx: *JSContext,
                                 public_id: public_id,
                                 system_id: system_id,
                                 force_quirks: _ } = doctype;
-            let node = DocumentType::new(name,
-                                         public_id,
-                                         system_id,
-                                         document);
+            let doctype_node = DocumentType::new(name, public_id, system_id, document);
             unsafe {
-                node.to_hubbub_node()
+                doctype_node.to_hubbub_node()
             }
         },
         create_element: |tag: ~hubbub::Tag| {
             debug!("create element");
-            let node = build_element_from_tag(tag.name.clone(), document);
+            let mut element = build_element_from_tag(tag.name.clone(), document);
 
             debug!("-- attach attrs");
-            node.as_mut_element(|element| {
-                for attr in tag.attributes.iter() {
-                    element.set_attr(node,
-                                     attr.name.clone(),
-                                     attr.value.clone());
-                }
-            });
+            for attr in tag.attributes.iter() {
+                let elem = element.clone();
+                element.get_mut().set_attr(&elem,
+                                             attr.name.clone(),
+                                             attr.value.clone());
+            }
 
             // Spawn additional parsing, network loads, etc. from tag and attrs
-            match node.type_id() {
+            match element.get().node.type_id {
                 // Handle CSS style sheets from <link> elements
                 ElementNodeTypeId(HTMLLinkElementTypeId) => {
-                    node.with_imm_element(|element| {
-                        match (element.get_attribute(Null, "rel"), element.get_attribute(Null, "href")) {
-                            (Some(rel), Some(href)) => {
-                                if "stylesheet" == rel.value_ref() {
-                                    debug!("found CSS stylesheet: {:s}", href.value_ref());
-                                    let url = parse_url(href.value_ref(), Some(url2.clone()));
-                                    css_chan2.send(CSSTaskNewFile(UrlProvenance(url)));
-                                }
+                    match (element.get().get_attribute(Null, "rel"),
+                           element.get().get_attribute(Null, "href")) {
+                        (Some(rel), Some(href)) => {
+                            if "stylesheet" == rel.get().value_ref() {
+                                debug!("found CSS stylesheet: {:s}", href.get().value_ref());
+                                let url = parse_url(href.get().value_ref(), Some(url2.clone()));
+                                css_chan2.send(CSSTaskNewFile(UrlProvenance(url)));
                             }
-                            _ => {}
                         }
-                    });
+                        _ => {}
+                    }
                 }
 
                 ElementNodeTypeId(HTMLIframeElementTypeId) => {
                     let iframe_chan = discovery_chan.clone();
-                    node.with_mut_iframe_element(|iframe_element| {
-                        let sandboxed = iframe_element.is_sandboxed();
-                        let elem = &mut iframe_element.htmlelement.element;
-                        let src_opt = elem.get_attribute(Null, "src").map(|x| x.Value());
-                        for src in src_opt.iter() {
-                            let iframe_url = parse_url(*src, Some(url2.clone()));
-                            iframe_element.frame = Some(iframe_url.clone());
-                            
-                            // Subpage Id
-                            let subpage_id = next_subpage_id.get();
-                            next_subpage_id.set(SubpageId(*subpage_id + 1));
-
-                            // Pipeline Id
-                            let pipeline_id = {
-                                let page = page_from_context(cx);
-                                unsafe { (*page).id }
-                            };
-
-                            iframe_element.size = Some(IFrameSize {
-                                pipeline_id: pipeline_id,
-                                subpage_id: subpage_id,
-                            });
-                            iframe_chan.send(HtmlDiscoveredIFrame((iframe_url,
-                                                                   subpage_id,
-                                                                   sandboxed)));
-                        }
-                    });
+                    let mut iframe_element: JS<HTMLIFrameElement> =
+                        HTMLIFrameElementCast::to(&element);
+                    let sandboxed = iframe_element.get().is_sandboxed();
+                    let elem: JS<Element> = ElementCast::from(&iframe_element);
+                    let src_opt = elem.get().get_attribute(Null, "src").map(|x| x.get().Value());
+                    for src in src_opt.iter() {
+                        let iframe_url = parse_url(*src, Some(url2.clone()));
+                        iframe_element.get_mut().extra.frame = Some(iframe_url.clone());
+
+                        // Subpage Id
+                        let subpage_id = next_subpage_id.get();
+                        next_subpage_id.set(SubpageId(*subpage_id + 1));
+
+                        // Pipeline Id
+                        let pipeline_id = {
+                            let page = page_from_context(cx);
+                            unsafe { (*page).id }
+                        };
+
+                        iframe_element.get_mut().size = Some(IFrameSize {
+                            pipeline_id: pipeline_id,
+                            subpage_id: subpage_id,
+                        });
+                        iframe_chan.send(HtmlDiscoveredIFrame((iframe_url,
+                                                               subpage_id,
+                                                               sandboxed)));
+                    }
                 }
 
                 //FIXME: This should be taken care of by set_attr, but we don't have
                 //       access to a window so HTMLImageElement::AfterSetAttr bails.
                 ElementNodeTypeId(HTMLImageElementTypeId) => {
-                    node.with_mut_image_element(|image_element| {
-                        image_element.update_image(image_cache_task.clone(), Some(url2.clone()));
-                    });
+                    let mut image_element: JS<HTMLImageElement> = HTMLImageElementCast::to(&element);
+                    image_element.get_mut().update_image(image_cache_task.clone(), Some(url2.clone()));
                 }
                 _ => {}
             }
 
-            unsafe { node.to_hubbub_node() }
+            unsafe { element.to_hubbub_node() }
         },
         create_text: |data: ~str| {
             debug!("create text");
@@ -407,9 +404,9 @@ pub fn parse_html(cx: *JSContext,
         append_child: |parent: hubbub::NodeDataPtr, child: hubbub::NodeDataPtr| {
             unsafe {
                 debug!("append child {:x} {:x}", parent, child);
-                let parent: AbstractNode = NodeWrapping::from_hubbub_node(parent);
-                let child: AbstractNode = NodeWrapping::from_hubbub_node(child);
-                parent.AppendChild(child);
+                let mut parent: JS<Node> = NodeWrapping::from_hubbub_node(parent);
+                let mut child: JS<Node> = NodeWrapping::from_hubbub_node(child);
+                parent.AppendChild(&mut child);
             }
             child
         },
@@ -446,51 +443,48 @@ pub fn parse_html(cx: *JSContext,
         },
         set_quirks_mode: |mode| {
             debug!("set quirks mode");
-            document.mut_document().set_quirks_mode(mode);
+            document.get_mut().set_quirks_mode(mode);
         },
         encoding_change: |encname| {
             debug!("encoding change");
-            document.mut_document().set_encoding_name(encname);
+            document.get_mut().set_encoding_name(encname);
         },
         complete_script: |script| {
             unsafe {
-                let scriptnode: AbstractNode = NodeWrapping::from_hubbub_node(script);
-                scriptnode.with_imm_element(|script| {
-                    match script.get_attribute(Null, "src") {
-                        Some(src) => {
-                            debug!("found script: {:s}", src.Value());
-                            let new_url = parse_url(src.value_ref(), Some(url3.clone()));
-                            js_chan2.send(JSTaskNewFile(new_url));
+                let script: JS<Element> = NodeWrapping::from_hubbub_node(script);
+                match script.get().get_attribute(Null, "src") {
+                    Some(src) => {
+                        debug!("found script: {:s}", src.get().Value());
+                        let new_url = parse_url(src.get().value_ref(), Some(url3.clone()));
+                        js_chan2.send(JSTaskNewFile(new_url));
+                    }
+                    None => {
+                        let mut data = ~[];
+                        let scriptnode: JS<Node> = NodeCast::from(&script);
+                        debug!("iterating over children {:?}", scriptnode.first_child());
+                        for child in scriptnode.children() {
+                            debug!("child = {:?}", child);
+                            let text: JS<Text> = TextCast::to(&child);
+                            data.push(text.get().characterdata.data.to_str());  // FIXME: Bad copy.
                         }
-                        None => {
-                            let mut data = ~[];
-                            debug!("iterating over children {:?}", scriptnode.first_child());
-                            for child in scriptnode.children() {
-                                debug!("child = {:?}", child);
-                                child.with_imm_text(|text| {
-                                    data.push(text.characterdata.data.to_str());  // FIXME: Bad copy.
-                                });
-                            }
 
-                            debug!("script data = {:?}", data);
-                            js_chan2.send(JSTaskNewInlineScript(data.concat(), url3.clone()));
-                        }
+                        debug!("script data = {:?}", data);
+                        js_chan2.send(JSTaskNewInlineScript(data.concat(), url3.clone()));
                     }
-                });
+                }
             }
             debug!("complete script");
         },
         complete_style: |style| {
             // We've reached the end of a <style> so we can submit all the text to the parser.
             unsafe {
-                let style: AbstractNode = NodeWrapping::from_hubbub_node(style);
+                let style: JS<Node> = NodeWrapping::from_hubbub_node(style);
                 let mut data = ~[];
                 debug!("iterating over children {:?}", style.first_child());
                 for child in style.children() {
                     debug!("child = {:?}", child);
-                    child.with_imm_text(|text| {
-                        data.push(text.characterdata.data.to_str());  // FIXME: Bad copy.
-                    });
+                    let text: JS<Text> = TextCast::to(&child);
+                    data.push(text.get().characterdata.data.to_str());  // FIXME: Bad copy.
                 }
 
                 debug!("style data = {:?}", data);
diff --git a/src/components/script/layout_interface.rs b/src/components/script/layout_interface.rs
index 8f6688b84aa..6ebea1809af 100644
--- a/src/components/script/layout_interface.rs
+++ b/src/components/script/layout_interface.rs
@@ -6,7 +6,7 @@
 /// coupling between these two components, and enables the DOM to be placed in a separate crate
 /// from layout.
 
-use dom::node::{AbstractNode, LayoutDataRef};
+use dom::node::LayoutDataRef;
 
 use extra::url::Url;
 use geom::point::Point2D;
@@ -52,14 +52,18 @@ pub enum Msg {
 /// Synchronous messages that script can send to layout.
 pub enum LayoutQuery {
     /// Requests the dimensions of the content box, as in the `getBoundingClientRect()` call.
-    ContentBoxQuery(AbstractNode, Chan<ContentBoxResponse>),
+    ContentBoxQuery(TrustedNodeAddress, Chan<ContentBoxResponse>),
     /// Requests the dimensions of all the content boxes, as in the `getClientRects()` call.
-    ContentBoxesQuery(AbstractNode, Chan<ContentBoxesResponse>),
+    ContentBoxesQuery(TrustedNodeAddress, Chan<ContentBoxesResponse>),
     /// Requests the node containing the point of interest
-    HitTestQuery(AbstractNode, Point2D<f32>, Chan<Result<HitTestResponse, ()>>),
-    MouseOverQuery(AbstractNode, Point2D<f32>, Chan<Result<MouseOverResponse, ()>>),
+    HitTestQuery(TrustedNodeAddress, Point2D<f32>, Chan<Result<HitTestResponse, ()>>),
+    MouseOverQuery(TrustedNodeAddress, Point2D<f32>, Chan<Result<MouseOverResponse, ()>>),
 }
 
+/// The address of a node known to be valid. These must only be sent from content -> layout,
+/// because we do not trust layout.
+pub type TrustedNodeAddress = *c_void;
+
 /// The address of a node. Layout sends these back. They must be validated via
 /// `from_untrusted_node_address` before they can be used, because we do not trust layout.
 pub type UntrustedNodeAddress = *c_void;
@@ -92,7 +96,7 @@ impl DocumentDamageLevel {
 /// Note that this is fairly coarse-grained and is separate from layout's notion of the document
 pub struct DocumentDamage {
     /// The topmost node in the tree that has changed.
-    root: AbstractNode,
+    root: TrustedNodeAddress,
     /// The amount of damage that occurred.
     level: DocumentDamageLevel,
 }
@@ -109,7 +113,7 @@ pub enum ReflowGoal {
 /// Information needed for a reflow.
 pub struct Reflow {
     /// The document node.
-    document_root: AbstractNode,
+    document_root: TrustedNodeAddress,
     /// The style changes that need to be done.
     damage: DocumentDamage,
     /// The goal of reflow: either to render to the screen or to flush layout info for script.
diff --git a/src/components/script/script.rs b/src/components/script/script.rs
index 5d270cf2e36..1d23dfc3402 100644
--- a/src/components/script/script.rs
+++ b/src/components/script/script.rs
@@ -26,18 +26,22 @@ mod macros;
 
 pub mod dom {
     pub mod bindings {
+        pub mod js;
         pub mod element;
-        pub mod node;
         pub mod utils;
         pub mod callback;
         pub mod conversions;
         pub mod proxyhandler;
+        pub mod trace;
         pub mod codegen {
             pub use self::BindingDeclarations::*;
             pub mod InterfaceTypes;
+            pub mod InheritTypes;
             pub mod PrototypeList;
             pub mod RegisterBindings;
             pub mod BindingDeclarations;
+            pub mod UnionConversions;
+            pub mod UnionTypes;
         }
     }
 
@@ -79,7 +83,6 @@ pub mod dom {
     pub mod htmldirectoryelement;
     pub mod htmldivelement;
     pub mod htmldlistelement;
-    pub mod htmldocument;
     pub mod htmlelement;
     pub mod htmlembedelement;
     pub mod htmlfieldsetelement;
diff --git a/src/components/script/script_task.rs b/src/components/script/script_task.rs
index 8a56291b95f..a9a284ad21f 100644
--- a/src/components/script/script_task.rs
+++ b/src/components/script/script_task.rs
@@ -6,14 +6,15 @@
 //! and layout tasks.
 
 use dom::bindings::codegen::RegisterBindings;
-use dom::bindings::utils::{Reflectable, GlobalStaticData};
-use dom::document::AbstractDocument;
+use dom::bindings::codegen::InheritTypes::{EventTargetCast, NodeCast, ElementCast};
+use dom::bindings::js::JS;
+use dom::bindings::utils::{Reflectable, GlobalStaticData, with_gc_enabled};
+use dom::document::{Document, HTMLDocument};
 use dom::element::Element;
 use dom::event::{Event_, ResizeEvent, ReflowEvent, ClickEvent, MouseDownEvent, MouseMoveEvent, MouseUpEvent};
 use dom::event::Event;
-use dom::eventtarget::AbstractEventTarget;
-use dom::htmldocument::HTMLDocument;
-use dom::node::AbstractNode;
+use dom::eventtarget::EventTarget;
+use dom::node::{Node, NodeHelpers};
 use dom::window::{TimerData, TimerHandle, Window};
 use html::hubbub_html_parser::HtmlParserResult;
 use html::hubbub_html_parser::{HtmlDiscoveredStyle, HtmlDiscoveredIFrame, HtmlDiscoveredScript};
@@ -32,7 +33,7 @@ use geom::size::Size2D;
 use js::JSVAL_NULL;
 use js::global::debug_fns;
 use js::glue::RUST_JSVAL_TO_OBJECT;
-use js::jsapi::{JSContext, JSObject};
+use js::jsapi::{JSContext, JSObject, JS_InhibitGC, JS_AllowGC};
 use js::jsapi::{JS_CallFunctionValue, JS_GetContextPrivate};
 use js::rust::{Compartment, Cx};
 use js;
@@ -52,6 +53,8 @@ use std::ptr;
 use std::task;
 use std::util::replace;
 
+use extra::serialize::{Encoder, Encodable};
+
 /// Messages used to control the script task.
 pub enum ScriptMsg {
     /// Loads a new URL on the specified pipeline.
@@ -86,6 +89,11 @@ pub struct NewLayoutInfo {
 #[deriving(Clone)]
 pub struct ScriptChan(SharedChan<ScriptMsg>);
 
+impl<S: Encoder> Encodable<S> for ScriptChan {
+    fn encode(&self, _s: &mut S) {
+    }
+}
+
 impl ScriptChan {
     /// Creates a new script chan.
     pub fn new() -> (Port<ScriptMsg>, ScriptChan) {
@@ -131,7 +139,13 @@ pub struct Page {
     resize_event: Option<Size2D<uint>>,
 
     /// Pending scroll to fragment event, if any
-    fragment_node: Option<AbstractNode>
+    fragment_node: Option<JS<Element>>
+}
+
+impl<S: Encoder> Encodable<S> for Page {
+    fn encode(&self, s: &mut S) {
+        self.fragment_node.encode(s);
+   }
 }
 
 pub struct PageTree {
@@ -223,23 +237,24 @@ impl Page {
     pub fn damage(&mut self, level: DocumentDamageLevel) {
         let root = match self.frame {
             None => return,
-            Some(ref frame) => frame.document.document().GetDocumentElement()
+            Some(ref frame) => frame.document.get().GetDocumentElement()
         };
         match root {
             None => {},
             Some(root) => {
+                let root: JS<Node> = NodeCast::from(&root);
                 match self.damage {
                     None => {}
                     Some(ref mut damage) => {
                         // FIXME(pcwalton): This is wrong. We should trace up to the nearest ancestor.
-                        damage.root = root;
+                        damage.root = root.to_trusted_node_address();
                         damage.level.add(level);
                         return
                     }
                 }
 
                 self.damage = Some(DocumentDamage {
-                    root: root,
+                    root: root.to_trusted_node_address(),
                     level: level,
                 })
             }
@@ -292,7 +307,7 @@ impl Page {
         let root = match self.frame {
             None => return,
             Some(ref frame) => {
-                frame.document.document().GetDocumentElement()
+                frame.document.get().GetDocumentElement()
             }
         };
 
@@ -314,8 +329,9 @@ impl Page {
                 self.last_reflow_id += 1;
 
                 // Send new document and relevant styles to layout.
+                let root: JS<Node> = NodeCast::from(&root);
                 let reflow = ~Reflow {
-                    document_root: root,
+                    document_root: root.to_trusted_node_address(),
                     url: self.url.get_ref().first().clone(),
                     goal: goal,
                     window_size: self.window_size,
@@ -333,6 +349,8 @@ impl Page {
     }
 
     pub fn initialize_js_info(&mut self, js_context: @Cx, global: *JSObject) {
+        assert!(global.is_not_null());
+
         // Note that the order that these variables are initialized is _not_ arbitrary. Switching
         // them around can -- and likely will -- lead to things breaking.
 
@@ -352,6 +370,8 @@ impl Page {
 
         unsafe {
             js_context.set_cx_private(page_ptr as *());
+
+            JS_InhibitGC(js_context.ptr);
         }
 
         self.js_info = Some(JSPageInfo {
@@ -363,11 +383,12 @@ impl Page {
 }
 
 /// Information for one frame in the browsing context.
+#[deriving(Encodable)]
 pub struct Frame {
     /// The document for this frame.
-    document: AbstractDocument,
+    document: JS<Document>,
     /// The window object for this frame.
-    window: @mut Window,
+    window: JS<Window>,
 }
 
 /// Encapsulation of the javascript information associated with each frame.
@@ -406,7 +427,7 @@ pub struct ScriptTask {
     /// The JavaScript runtime.
     js_runtime: js::rust::rt,
 
-    mouse_over_targets:Option<~[AbstractNode]>
+    mouse_over_targets: Option<~[JS<Node>]>
 }
 
 /// Returns the relevant page from the associated JS Context.
@@ -565,28 +586,27 @@ impl ScriptTask {
     fn handle_fire_timer_msg(&mut self, id: PipelineId, timer_data: ~TimerData) {
         let page = self.page_tree.find(id).expect("ScriptTask: received fire timer msg for a
             pipeline ID not associated with this script task. This is a bug.").page;
-        let window = page.frame.expect("ScriptTask: Expect a timeout to have a document").window;
-        if !window.active_timers.contains(&TimerHandle { handle: timer_data.handle, cancel_chan: None }) {
+        let mut window = page.frame.get_ref().window.clone();
+        if !window.get().active_timers.contains(&TimerHandle { handle: timer_data.handle, cancel_chan: None }) {
             return;
         }
-        window.active_timers.remove(&TimerHandle { handle: timer_data.handle, cancel_chan: None });
-        unsafe {
-            let this_value = if timer_data.args.len() > 0 {
+        window.get_mut().active_timers.remove(&TimerHandle { handle: timer_data.handle, cancel_chan: None });
+        let this_value = if timer_data.args.len() > 0 {
+            unsafe {
                 RUST_JSVAL_TO_OBJECT(timer_data.args[0])
-            } else {
-                page.js_info.get_ref().js_compartment.global_obj.ptr
-            };
-
-            // TODO: Support extra arguments. This requires passing a `*JSVal` array as `argv`.
-            let rval = JSVAL_NULL;
-            JS_CallFunctionValue(page.js_info.get_ref().js_context.ptr,
-                                 this_value,
-                                 timer_data.funval,
-                                 0,
-                                 ptr::null(),
-                                 &rval);
+            }
+        } else {
+            page.js_info.get_ref().js_compartment.global_obj.ptr
+        };
 
-        }
+        // TODO: Support extra arguments. This requires passing a `*JSVal` array as `argv`.
+        let rval = JSVAL_NULL;
+        let cx = page.js_info.get_ref().js_context.ptr;
+        with_gc_enabled(cx, || {
+            unsafe {
+                JS_CallFunctionValue(cx, this_value, timer_data.funval, 0, ptr::null(), &rval);
+            }
+        });
     }
 
     /// Handles a notification that reflow completed.
@@ -697,9 +717,9 @@ impl ScriptTask {
         // Parse HTML.
         //
         // Note: We can parse the next document in parallel with any previous documents.
-        let document = HTMLDocument::new(window, Some(url.clone()));
+        let mut document = Document::new(&window, Some(url.clone()), HTMLDocument, None);
         let html_parsing_result = hubbub_html_parser::parse_html(cx.ptr,
-                                                                 document,
+                                                                 &mut document,
                                                                  url.clone(),
                                                                  self.resource_task.clone(),
                                                                  self.image_cache_task.clone(),
@@ -711,8 +731,8 @@ impl ScriptTask {
 
         // Create the root frame.
         page.frame = Some(Frame {
-            document: document,
-            window: window,
+            document: document.clone(),
+            window: window.clone(),
         });
 
         // Send style sheets over to layout.
@@ -747,7 +767,7 @@ impl ScriptTask {
         }
 
         // Kick off the initial reflow of the page.
-        document.document().content_changed();
+        document.get().content_changed();
 
         let fragment = url.fragment.as_ref().map(|ref fragment| fragment.to_owned());
 
@@ -766,47 +786,50 @@ impl ScriptTask {
 
         // Evaluate every script in the document.
         for file in js_scripts.iter() {
-            let _ = cx.evaluate_script(compartment.global_obj,
-                                       file.data.clone(),
-                                       file.url.to_str(),
-                                       1);
+            with_gc_enabled(cx.ptr, || {
+                cx.evaluate_script(compartment.global_obj,
+                                   file.data.clone(),
+                                   file.url.to_str(),
+                                   1);
+            });
         }
 
         // We have no concept of a document loader right now, so just dispatch the
         // "load" event as soon as we've finished executing all scripts parsed during
         // the initial load.
-        let event = Event::new(window);
-        event.mut_event().InitEvent(~"load", false, false);
-        let doctarget = AbstractEventTarget::from_document(document);
-        let wintarget = AbstractEventTarget::from_window(window);
-        window.eventtarget.dispatch_event_with_target(wintarget, Some(doctarget), event);
+        let mut event = Event::new(&window);
+        event.get_mut().InitEvent(~"load", false, false);
+        let doctarget = EventTargetCast::from(&document);
+        let mut wintarget: JS<EventTarget> = EventTargetCast::from(&window);
+        let winclone = wintarget.clone();
+        wintarget.get_mut().dispatch_event_with_target(&winclone, Some(doctarget), &mut event);
 
         page.fragment_node = fragment.map_default(None, |fragid| self.find_fragment_node(page, fragid));
 
         self.constellation_chan.send(LoadCompleteMsg(page.id, url));
     }
 
-    fn find_fragment_node(&self, page: &mut Page, fragid: ~str) -> Option<AbstractNode> {
-        let document = page.frame.expect("root frame is None").document; 
-        match document.document().GetElementById(fragid.to_owned()) {
+    fn find_fragment_node(&self, page: &mut Page, fragid: ~str) -> Option<JS<Element>> {
+        let document = page.frame.get_ref().document.clone();
+        match document.get().GetElementById(fragid.to_owned()) {
             Some(node) => Some(node),
             None => {
-                let doc_node = AbstractNode::from_document(document);
+                let doc_node: JS<Node> = NodeCast::from(&document);
                 let mut anchors = doc_node.traverse_preorder().filter(|node| node.is_anchor_element());
                 anchors.find(|node| {
-                    node.with_imm_element(|elem| {
-                        elem.get_attribute(Null, "name").map_default(false, |attr| {
-                            attr.value_ref() == fragid
-                        })
+                    let elem: JS<Element> = ElementCast::to(node);
+                    elem.get().get_attribute(Null, "name").map_default(false, |attr| {
+                        attr.get().value_ref() == fragid
                     })
-                })
+                }).map(|node| ElementCast::to(&node))
             }
         }
     }
 
-    fn scroll_fragment_point(&self, pipeline_id: PipelineId, page: &mut Page, node: AbstractNode) {
+    fn scroll_fragment_point(&self, pipeline_id: PipelineId, page: &mut Page, node: JS<Element>) {
         let (port, chan) = Chan::new();
-        match page.query_layout(ContentBoxQuery(node, chan), port) {
+        let node: JS<Node> = NodeCast::from(&node);
+        match page.query_layout(ContentBoxQuery(node.to_trusted_node_address(), chan), port) {
             ContentBoxResponse(rect) => {
                 let point = Point2D(to_frac_px(rect.origin.x).to_f32().unwrap(), 
                                     to_frac_px(rect.origin.y).to_f32().unwrap());
@@ -852,18 +875,19 @@ impl ScriptTask {
             ClickEvent(_button, point) => {
                 debug!("ClickEvent: clicked at {:?}", point);
 
-                let document = page.frame.expect("root frame is None").document;
-                let root = document.document().GetDocumentElement();
+                let document = page.frame.get_ref().document.clone();
+                let root = document.get().GetDocumentElement();
                 if root.is_none() {
                     return;
                 }
                 let (port, chan) = Chan::new();
-                match page.query_layout(HitTestQuery(root.unwrap(), point, chan), port) {
+                let root: JS<Node> = NodeCast::from(&root.unwrap());
+                match page.query_layout(HitTestQuery(root.to_trusted_node_address(), point, chan), port) {
                     Ok(HitTestResponse(node_address)) => {
                         debug!("node address is {:?}", node_address);
-                        let mut node = AbstractNode::from_untrusted_node_address(self.js_runtime
-                                                                                     .ptr,
-                                                                                 node_address);
+                        let mut node: JS<Node> =
+                            NodeHelpers::from_untrusted_node_address(self.js_runtime.ptr,
+                                                                     node_address);
                         debug!("clicked on {:s}", node.debug_str());
 
                         // Traverse node generations until a node that is an element is
@@ -876,11 +900,10 @@ impl ScriptTask {
                         }
 
                         if node.is_element() {
-                            node.with_imm_element(|element| {
-                                if "a" == element.tag_name {
-                                    self.load_url_from_element(page, element)
-                                }
-                            })
+                            let element: JS<Element> = ElementCast::to(&node);
+                            if "a" == element.get().tag_name {
+                                self.load_url_from_element(page, element.get())
+                            }
                         }
                     },
                     Err(()) => debug!("layout query error"),
@@ -889,21 +912,22 @@ impl ScriptTask {
             MouseDownEvent(..) => {}
             MouseUpEvent(..) => {}
             MouseMoveEvent(point) => {
-                let document = page.frame.expect("root frame is None").document;
-                let root = document.document().GetDocumentElement();
+                let document = page.frame.get_ref().document.clone();
+                let root = document.get().GetDocumentElement();
                 if root.is_none() {
                     return;
                 }
+                let root: JS<Node> = NodeCast::from(&root.unwrap());
                 let (port, chan) = Chan::new();
-                match page.query_layout(MouseOverQuery(root.unwrap(), point, chan), port) {
+                match page.query_layout(MouseOverQuery(root.to_trusted_node_address(), point, chan), port) {
                     Ok(MouseOverResponse(node_address)) => {
 
-                        let mut target_list:~[AbstractNode] = ~[];
+                        let mut target_list: ~[JS<Node>] = ~[];
                         let mut target_compare = false;
 
                         match self.mouse_over_targets {
                             Some(ref mut mouse_over_targets) => {
-                                for node in mouse_over_targets.iter() {
+                                for node in mouse_over_targets.mut_iter() {
                                     node.set_hover_state(false);
                                 }
                             }
@@ -911,9 +935,9 @@ impl ScriptTask {
                         }
 
                         for node_address in node_address.iter() {
-                            let mut node = AbstractNode::from_untrusted_node_address(self.js_runtime
-                                                                                         .ptr,
-                                                                                     *node_address);
+                            let mut node: JS<Node> =
+                                NodeHelpers::from_untrusted_node_address(
+                                self.js_runtime.ptr, *node_address);
                             // Traverse node generations until a node that is an element is
                             // found.
                             while !node.is_element() {
@@ -964,13 +988,13 @@ impl ScriptTask {
         // if the node's element is "a," load url from href attr
         let attr = element.get_attribute(Null, "href");
         for href in attr.iter() {
-            debug!("ScriptTask: clicked on link to {:s}", href.Value());
-            let click_frag = href.value_ref().starts_with("#");
+            debug!("ScriptTask: clicked on link to {:s}", href.get().Value());
+            let click_frag = href.get().value_ref().starts_with("#");
             let base_url = page.url.as_ref().map(|&(ref url, _)| {
                 url.clone()
             });
             debug!("ScriptTask: current url is {:?}", base_url);
-            let url = parse_url(href.value_ref(), base_url);
+            let url = parse_url(href.get().value_ref(), base_url);
 
             if click_frag {
                 match self.find_fragment_node(page, url.fragment.unwrap()) {
@@ -995,6 +1019,11 @@ fn shut_down_layout(page: @mut Page) {
 
     // Destroy all nodes. Setting frame and js_info to None will trigger our
     // compartment to shutdown, run GC, etc.
+
+    unsafe {
+        JS_AllowGC(page.js_info.get_ref().js_context.ptr);
+    }
+
     page.frame = None;
     page.js_info = None;
 
diff --git a/src/components/style/properties.rs.mako b/src/components/style/properties.rs.mako
index 0f2d9cb63e3..a9e4c0b03fd 100644
--- a/src/components/style/properties.rs.mako
+++ b/src/components/style/properties.rs.mako
@@ -18,8 +18,9 @@ pub use parsing_utils::*;
 pub use self::common_types::*;
 use selector_matching::MatchedProperty;
 
-pub mod common_types;
+use extra::serialize::{Encodable, Encoder};
 
+pub mod common_types;
 
 <%!
 
@@ -1025,6 +1026,11 @@ pub struct PropertyDeclarationBlock {
     normal: Arc<~[PropertyDeclaration]>,
 }
 
+impl<S: Encoder> Encodable<S> for PropertyDeclarationBlock {
+    fn encode(&self, _: &mut S) {
+    }
+}
+
 
 pub fn parse_style_attribute(input: &str, base_url: &Url) -> PropertyDeclarationBlock {
     parse_property_declaration_list(tokenize(input), base_url)
diff --git a/src/components/util/namespace.rs b/src/components/util/namespace.rs
index ff9eda169c9..b23b235bad0 100644
--- a/src/components/util/namespace.rs
+++ b/src/components/util/namespace.rs
@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#[deriving(Eq, Clone)]
+#[deriving(Eq, Clone, Encodable)]
 pub enum Namespace {
     Null,
     HTML,
diff --git a/src/components/gfx/opts.rs b/src/components/util/opts.rs
index 04daf519c87..2f1d9777b8a 100644
--- a/src/components/gfx/opts.rs
+++ b/src/components/util/opts.rs
@@ -46,6 +46,12 @@ pub struct Opts {
     output_file: Option<~str>,
     headless: bool,
     hard_fail: bool,
+
+    /// True if we should bubble intrinsic widths sequentially (`-b`). If this is true, then
+    /// intrinsic widths are computed as a separate pass instead of during flow construction. You
+    /// may wish to turn this flag on in order to benchmark style recalculation against other
+    /// browser engines.
+    bubble_widths_separately: bool,
 }
 
 fn print_usage(app: &str, opts: &[groups::OptGroup]) {
@@ -68,6 +74,7 @@ pub fn from_cmdline_args(args: &[~str]) -> Opts {
         groups::optopt("y", "layout-threads", "Number of threads to use for layout", "1"),
         groups::optflag("z", "headless", "Headless mode"),
         groups::optflag("f", "hard-fail", "Exit on task failure instead of displaying about:failure"),
+        groups::optflag("b", "bubble-widths", "Bubble intrinsic widths separately like other engines"),
         groups::optflag("h", "help", "Print this message")
     ];
 
@@ -143,5 +150,6 @@ pub fn from_cmdline_args(args: &[~str]) -> Opts {
         output_file: opt_match.opt_str("o"),
         headless: opt_match.opt_present("z"),
         hard_fail: opt_match.opt_present("f"),
+        bubble_widths_separately: opt_match.opt_present("b"),
     }
 }
diff --git a/src/components/util/util.rs b/src/components/util/util.rs
index 46b37ceb3be..9df491dfeb5 100644
--- a/src/components/util/util.rs
+++ b/src/components/util/util.rs
@@ -7,6 +7,7 @@
 
 #[feature(macro_rules, managed_boxes)];
 
+extern mod azure;
 extern mod extra;
 extern mod geom;
 extern mod native;
@@ -18,6 +19,7 @@ pub mod debug;
 pub mod geometry;
 pub mod io;
 pub mod namespace;
+pub mod opts;
 pub mod range;
 pub mod smallvec;
 pub mod sort;
diff --git a/src/support/spidermonkey/mozjs b/src/support/spidermonkey/mozjs
-Subproject 3e633e7e498e64793cb2c75394ed78d507c383a
+Subproject 6615c7e7d17a4f1a1c0c2adb39765082f5421b6
diff --git a/src/support/spidermonkey/rust-mozjs b/src/support/spidermonkey/rust-mozjs
-Subproject c2f282d8762aec1a55007ff75ef85dfb34e61e7
+Subproject 6a9db14da31271868090963067e1e689904e515
diff --git a/src/test/html/content/harness.js b/src/test/html/content/harness.js
index ade4536a879..72aa2712469 100644
--- a/src/test/html/content/harness.js
+++ b/src/test/html/content/harness.js
@@ -37,6 +37,24 @@ function is_function(val, name) {
   starts_with(String(val), "function " + name + "(");
 }
 
+function should_throw(f) {
+  try {
+    f();
+    _fail("operation should have thrown but did not");
+  } catch (x) {
+    _pass("operation successfully threw an exception", x.toString());
+  }
+}
+
+function should_not_throw(f) {
+  try {
+    f();
+    _pass("operation did not throw an exception");
+  } catch (x) {
+    _fail("operation should have not thrown", x.toString());
+  }
+}
+
 var _test_complete = false;
 var _test_timeout = 10000; //10 seconds
 function finish() {
diff --git a/src/test/html/content/test_documentElement.html b/src/test/html/content/test_documentElement.html
index eea379456b1..efe68e086d0 100644
--- a/src/test/html/content/test_documentElement.html
+++ b/src/test/html/content/test_documentElement.html
@@ -6,7 +6,6 @@ is_a(window, Window);
 is_a(document.documentElement, HTMLHtmlElement);
 is_a(document.documentElement.firstChild, HTMLHeadElement);
 is(document.documentElement.nextSibling, null);
-is_a(document, HTMLDocument);
 is_a(document, Document);
 finish();
 </script>
diff --git a/src/test/html/content/test_document_contenttype.html b/src/test/html/content/test_document_contenttype.html
index ede2696f98a..4a63a654547 100644
--- a/src/test/html/content/test_document_contenttype.html
+++ b/src/test/html/content/test_document_contenttype.html
@@ -5,14 +5,14 @@
         <script>
             // test1: HTML document
             {
-                is_a(document, HTMLDocument, "test1-0, HTML document");
+                is_a(document, Document, "test1-0, HTML document");
                 is(document.contentType, "text/html", "test1-1, HTML document");
             }
 
             // test2: XML document
             {
                 var doc = new Document;
-                is_not_a(doc, HTMLDocument, "test2-0, XML document");
+                is_a(doc, Document, "test2-0, XML document");
                 is(doc.contentType, "application/xml", "test2-1, XML document");
             }
 
diff --git a/src/test/html/content/test_document_implementation.html b/src/test/html/content/test_document_implementation.html
index 6f7ac8a89ab..57dabd13e71 100644
--- a/src/test/html/content/test_document_implementation.html
+++ b/src/test/html/content/test_document_implementation.html
@@ -27,7 +27,6 @@
                 var htmldoc = document.implementation.createHTMLDocument("example title");
                 isnot(htmldoc, null, "test3-0, createHTMLDocument");
                 is_a(htmldoc, Document, "test3-1, createHTMLDocument");
-                is_a(htmldoc, HTMLDocument, "test3-2, createHTMLDocument");
                 is(htmldoc.childNodes.length, 2, "test3-3, createHTMLDocument");
 
                 is_a(htmldoc.doctype && htmldoc.doctype, DocumentType, "test3-4, createHTMLDocument");
diff --git a/src/test/html/content/test_exception.html b/src/test/html/content/test_exception.html
index ed96fe22867..b2cfda177d4 100644
--- a/src/test/html/content/test_exception.html
+++ b/src/test/html/content/test_exception.html
@@ -1,11 +1,6 @@
 <!doctype html>
 <script src="harness.js"></script>
 <script>
-try {
-  document.createElement("1foo");
-  is(true, false, "No exception thrown");
-} catch (e) {
-  is(true, true, "Exception caught");
-}
+should_throw(function() { document.createElement("1foo") });
 finish();
 </script>
diff --git a/src/test/html/content/test_parentnodes.html b/src/test/html/content/test_parentnodes.html
index 0b1bb610414..2131b7270b2 100644
--- a/src/test/html/content/test_parentnodes.html
+++ b/src/test/html/content/test_parentnodes.html
@@ -6,7 +6,7 @@
 <body>
   <div id="div1"></div>
   <script>
-    is_a(document.documentElement.parentNode, HTMLDocument);
+    is_a(document.documentElement.parentNode, Document);
     is(document.documentElement.parentElement, null);
 
     var elem = document.createElement("p");
diff --git a/src/test/html/content/test_prototypes.html b/src/test/html/content/test_prototypes.html
index 11ee11242b5..93019abe424 100644
--- a/src/test/html/content/test_prototypes.html
+++ b/src/test/html/content/test_prototypes.html
@@ -5,6 +5,7 @@
 <body>
   <foo-á>foo</foo-á>
 <script>
+is_a(window.document, Node);
 gc(); // ensure that our document rooting works; subsequent accesses should be valid.
 is_a(window.document, Node);
 is(window.document.nodeType, Node.DOCUMENT_NODE);
@@ -13,7 +14,6 @@ is_a(window.document.documentElement, Element);
 is_a(window.document.documentElement, HTMLElement);
 is_a(window.document.documentElement, HTMLHtmlElement);
 is_a(window.document, Document);
-is_a(window.document, HTMLDocument);
 is(window.document.documentElement.tagName, "HTML");
 is_a(window.document.getElementsByTagName('foo-á')[0], HTMLUnknownElement);
 is(window.document.getElementsByTagName('foo-á')[0].tagName, "FOO-á");
diff --git a/src/test/html/content/test_union.html b/src/test/html/content/test_union.html
new file mode 100644
index 00000000000..d5483ad8a3a
--- /dev/null
+++ b/src/test/html/content/test_union.html
@@ -0,0 +1,26 @@
+<html>
+<head>
+<script src="harness.js"></script>
+<select id="sel"></select>
+<script>
+  var div = document.createElement('div');
+  var optgroup = document.createElement('optgroup');
+  var sel = document.getElementById('sel');
+
+  should_not_throw(function() {
+    var opt = document.createElement('option');
+    sel.add(opt);
+    sel.add(optgroup);
+    sel.add(opt, div);
+    sel.add(optgroup, div);
+    sel.add(opt, 5);
+    sel.add(optgroup, 5);
+  });
+
+  should_throw(function() { sel.add(div) });
+  should_throw(function() { sel.add(optgroup, function() {}) });
+
+  finish();
+</script>
+</head>
+</html>