task -> thread

1 files changed, 0 insertions, 2247 deletions

diff --git a/components/script/script_task.rs b/components/script/script_task.rs
deleted file mode 100644
index 910d1e785f8..00000000000
--- a/components/script/script_task.rs
+++ /dev/null
@@ -1,2247 +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/. */
-
-//! The script task is the task that owns the DOM in memory, runs JavaScript, and spawns parsing
-//! and layout tasks. It's in charge of processing events for all same-origin pages in a frame
-//! tree, and manages the entire lifetime of pages in the frame tree from initial request to
-//! teardown.
-//!
-//! Page loads follow a two-step process. When a request for a new page load is received, the
-//! network request is initiated and the relevant data pertaining to the new page is stashed.
-//! While the non-blocking request is ongoing, the script task is free to process further events,
-//! noting when they pertain to ongoing loads (such as resizes/viewport adjustments). When the
-//! initial response is received for an ongoing load, the second phase starts - the frame tree
-//! entry is created, along with the Window and Document objects, and the appropriate parser
-//! takes over the response body. Once parsing is complete, the document lifecycle for loading
-//! a page runs its course and the script task returns to processing events in the main event
-//! loop.
-
-use devtools;
-use devtools_traits::{DevtoolScriptControlMsg, DevtoolsPageInfo};
-use devtools_traits::{ScriptToDevtoolsControlMsg, WorkerId};
-use document_loader::DocumentLoader;
-use dom::bindings::cell::DOMRefCell;
-use dom::bindings::codegen::Bindings::DocumentBinding::{DocumentMethods, DocumentReadyState};
-use dom::bindings::conversions::{FromJSValConvertible, StringificationBehavior};
-use dom::bindings::global::GlobalRef;
-use dom::bindings::inheritance::Castable;
-use dom::bindings::js::{JS, RootCollection, trace_roots};
-use dom::bindings::js::{RootCollectionPtr, RootedReference};
-use dom::bindings::refcounted::{LiveDOMReferences, Trusted, TrustedReference, trace_refcounted_objects};
-use dom::bindings::trace::{JSTraceable, RootedVec, trace_traceables};
-use dom::bindings::utils::{DOM_CALLBACKS, WRAP_CALLBACKS};
-use dom::document::{Document, DocumentProgressHandler, DocumentSource, FocusType, IsHTMLDocument};
-use dom::element::Element;
-use dom::event::{Event, EventBubbles, EventCancelable};
-use dom::htmlanchorelement::HTMLAnchorElement;
-use dom::node::{Node, NodeDamage, window_from_node};
-use dom::servohtmlparser::{ParserContext, ParserRoot};
-use dom::uievent::UIEvent;
-use dom::window::{ReflowReason, ScriptHelpers, Window};
-use dom::worker::TrustedWorkerAddress;
-use euclid::Rect;
-use euclid::point::Point2D;
-use gfx_traits::LayerId;
-use hyper::header::{ContentType, HttpDate};
-use hyper::header::{Headers, LastModified};
-use hyper::method::Method;
-use hyper::mime::{Mime, SubLevel, TopLevel};
-use ipc_channel::ipc::{self, IpcSender};
-use ipc_channel::router::ROUTER;
-use js::glue::CollectServoSizes;
-use js::jsapi::{DOMProxyShadowsResult, HandleId, HandleObject, RootedValue};
-use js::jsapi::{DisableIncrementalGC, JS_AddExtraGCRootsTracer, JS_SetWrapObjectCallbacks};
-use js::jsapi::{GCDescription, GCProgress, JSGCInvocationKind, SetGCSliceCallback};
-use js::jsapi::{JSAutoRequest, JSGCStatus, JS_GetRuntime, JS_SetGCCallback, SetDOMCallbacks};
-use js::jsapi::{JSContext, JSRuntime, JSTracer};
-use js::jsapi::{JSObject, SetPreserveWrapperCallback};
-use js::jsval::UndefinedValue;
-use js::rust::Runtime;
-use layout_interface::{ReflowQueryType};
-use layout_interface::{self, LayoutChan, NewLayoutTaskInfo, ReflowGoal, ScriptLayoutChan};
-use libc;
-use mem::heap_size_of_self_and_children;
-use msg::constellation_msg::{ConstellationChan, LoadData};
-use msg::constellation_msg::{MouseButton, MouseEventType, MozBrowserEvent, PipelineId};
-use msg::constellation_msg::{PipelineNamespace};
-use msg::constellation_msg::{SubpageId, WindowSizeData};
-use msg::webdriver_msg::WebDriverScriptCommand;
-use net_traits::LoadData as NetLoadData;
-use net_traits::image_cache_task::{ImageCacheChan, ImageCacheResult, ImageCacheTask};
-use net_traits::storage_task::StorageTask;
-use net_traits::{AsyncResponseTarget, ControlMsg, LoadConsumer, LoadContext, Metadata, ResourceTask};
-use network_listener::NetworkListener;
-use page::{Frame, IterablePage, Page};
-use parse::html::{ParseContext, parse_html};
-use parse::xml::{self, parse_xml};
-use profile_traits::mem::{self, OpaqueSender, Report, ReportKind, ReportsChan};
-use profile_traits::time::{self, ProfilerCategory, profile};
-use script_traits::CompositorEvent::{KeyEvent, MouseButtonEvent, MouseMoveEvent, ResizeEvent};
-use script_traits::CompositorEvent::{TouchEvent};
-use script_traits::{CompositorEvent, ConstellationControlMsg, EventResult, InitialScriptState, NewLayoutInfo};
-use script_traits::{LayoutMsg, OpaqueScriptLayoutChannel, ScriptMsg as ConstellationMsg};
-use script_traits::{ScriptTaskFactory, ScriptToCompositorMsg, TimerEvent, TimerEventRequest, TimerSource};
-use script_traits::{TouchEventType, TouchId};
-use std::any::Any;
-use std::borrow::ToOwned;
-use std::cell::{Cell, RefCell};
-use std::collections::HashSet;
-use std::io::{Write, stdout};
-use std::marker::PhantomData;
-use std::mem as std_mem;
-use std::option::Option;
-use std::ptr;
-use std::rc::Rc;
-use std::result::Result;
-use std::sync::atomic::{Ordering, AtomicBool};
-use std::sync::mpsc::{Receiver, Select, Sender, channel};
-use std::sync::{Arc, Mutex};
-use time::{Tm, now};
-use url::Url;
-use util::opts;
-use util::str::DOMString;
-use util::task;
-use util::task_state;
-use webdriver_handlers;
-
-thread_local!(pub static STACK_ROOTS: Cell<Option<RootCollectionPtr>> = Cell::new(None));
-thread_local!(static SCRIPT_TASK_ROOT: RefCell<Option<*const ScriptTask>> = RefCell::new(None));
-
-unsafe extern fn trace_rust_roots(tr: *mut JSTracer, _data: *mut libc::c_void) {
-    SCRIPT_TASK_ROOT.with(|root| {
-        if let Some(script_task) = *root.borrow() {
-            (*script_task).trace(tr);
-        }
-    });
-
-    trace_traceables(tr);
-    trace_roots(tr);
-}
-
-/// A document load that is in the process of fetching the requested resource. Contains
-/// data that will need to be present when the document and frame tree entry are created,
-/// but is only easily available at initiation of the load and on a push basis (so some
-/// data will be updated according to future resize events, viewport changes, etc.)
-#[derive(JSTraceable)]
-struct InProgressLoad {
-    /// The pipeline which requested this load.
-    pipeline_id: PipelineId,
-    /// The parent pipeline and child subpage associated with this load, if any.
-    parent_info: Option<(PipelineId, SubpageId)>,
-    /// The current window size associated with this pipeline.
-    window_size: Option<WindowSizeData>,
-    /// Channel to the layout task associated with this pipeline.
-    layout_chan: LayoutChan,
-    /// The current viewport clipping rectangle applying to this pipeline, if any.
-    clip_rect: Option<Rect<f32>>,
-    /// Window is frozen (navigated away while loading for example).
-    is_frozen: bool,
-    /// The requested URL of the load.
-    url: Url,
-}
-
-impl InProgressLoad {
-    /// Create a new InProgressLoad object.
-    fn new(id: PipelineId,
-           parent_info: Option<(PipelineId, SubpageId)>,
-           layout_chan: LayoutChan,
-           window_size: Option<WindowSizeData>,
-           url: Url) -> InProgressLoad {
-        InProgressLoad {
-            pipeline_id: id,
-            parent_info: parent_info,
-            layout_chan: layout_chan,
-            window_size: window_size,
-            clip_rect: None,
-            is_frozen: false,
-            url: url,
-        }
-    }
-}
-
-/// Encapsulated state required to create cancellable runnables from non-script threads.
-pub struct RunnableWrapper {
-    pub cancelled: Arc<AtomicBool>,
-}
-
-impl RunnableWrapper {
-    pub fn wrap_runnable<T: Runnable + Send + 'static>(&self, runnable: T) -> Box<Runnable + Send> {
-        box CancellableRunnable {
-            cancelled: self.cancelled.clone(),
-            inner: box runnable,
-        }
-    }
-}
-
-/// A runnable that can be discarded by toggling a shared flag.
-pub struct CancellableRunnable<T: Runnable + Send> {
-    cancelled: Arc<AtomicBool>,
-    inner: Box<T>,
-}
-
-impl<T: Runnable + Send> Runnable for CancellableRunnable<T> {
-    fn is_cancelled(&self) -> bool {
-        self.cancelled.load(Ordering::Relaxed)
-    }
-
-    fn handler(self: Box<CancellableRunnable<T>>) {
-        self.inner.handler()
-    }
-}
-
-pub trait Runnable {
-    fn is_cancelled(&self) -> bool { false }
-    fn handler(self: Box<Self>);
-}
-
-pub trait MainThreadRunnable {
-    fn handler(self: Box<Self>, script_task: &ScriptTask);
-}
-
-enum MixedMessage {
-    FromConstellation(ConstellationControlMsg),
-    FromScript(MainThreadScriptMsg),
-    FromDevtools(DevtoolScriptControlMsg),
-    FromImageCache(ImageCacheResult),
-    FromScheduler(TimerEvent),
-}
-
-/// Common messages used to control the event loops in both the script and the worker
-pub enum CommonScriptMsg {
-    /// Requests that the script task measure its memory usage. The results are sent back via the
-    /// supplied channel.
-    CollectReports(ReportsChan),
-    /// A DOM object's last pinned reference was removed (dispatched to all tasks).
-    RefcountCleanup(TrustedReference),
-    /// Generic message that encapsulates event handling.
-    RunnableMsg(ScriptTaskEventCategory, Box<Runnable + Send>),
-}
-
-#[derive(Clone, Copy, Debug, Eq, Hash, JSTraceable, PartialEq)]
-pub enum ScriptTaskEventCategory {
-    AttachLayout,
-    ConstellationMsg,
-    DevtoolsMsg,
-    DocumentEvent,
-    DomEvent,
-    FileRead,
-    ImageCacheMsg,
-    InputEvent,
-    NetworkEvent,
-    Resize,
-    ScriptEvent,
-    TimerEvent,
-    SetViewport,
-    StylesheetLoad,
-    UpdateReplacedElement,
-    WebSocketEvent,
-    WorkerEvent,
-}
-
-/// Messages used to control the script event loop
-pub enum MainThreadScriptMsg {
-    /// Common variants associated with the script messages
-    Common(CommonScriptMsg),
-    /// Notify a document that all pending loads are complete.
-    DocumentLoadsComplete(PipelineId),
-    /// Notifies the script that a window associated with a particular pipeline
-    /// should be closed (only dispatched to ScriptTask).
-    ExitWindow(PipelineId),
-    /// Generic message for running tasks in the ScriptTask
-    MainThreadRunnableMsg(Box<MainThreadRunnable + Send>),
-    /// Begins a content-initiated load on the specified pipeline (only
-    /// dispatched to ScriptTask).
-    Navigate(PipelineId, LoadData),
-}
-
-/// A cloneable interface for communicating with an event loop.
-pub trait ScriptChan {
-    /// Send a message to the associated event loop.
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()>;
-    /// Clone this handle.
-    fn clone(&self) -> Box<ScriptChan + Send>;
-}
-
-impl OpaqueSender<CommonScriptMsg> for Box<ScriptChan + Send> {
-    fn send(&self, msg: CommonScriptMsg) {
-        ScriptChan::send(&**self, msg).unwrap();
-    }
-}
-
-/// An interface for receiving ScriptMsg values in an event loop. Used for synchronous DOM
-/// APIs that need to abstract over multiple kinds of event loops (worker/main thread) with
-/// different Receiver interfaces.
-pub trait ScriptPort {
-    fn recv(&self) -> CommonScriptMsg;
-}
-
-impl ScriptPort for Receiver<CommonScriptMsg> {
-    fn recv(&self) -> CommonScriptMsg {
-        self.recv().unwrap()
-    }
-}
-
-impl ScriptPort for Receiver<MainThreadScriptMsg> {
-    fn recv(&self) -> CommonScriptMsg {
-        match self.recv().unwrap() {
-            MainThreadScriptMsg::Common(script_msg) => script_msg,
-            _ => panic!("unexpected main thread event message!")
-        }
-    }
-}
-
-impl ScriptPort for Receiver<(TrustedWorkerAddress, CommonScriptMsg)> {
-    fn recv(&self) -> CommonScriptMsg {
-        self.recv().unwrap().1
-    }
-}
-
-impl ScriptPort for Receiver<(TrustedWorkerAddress, MainThreadScriptMsg)> {
-    fn recv(&self) -> CommonScriptMsg {
-        match self.recv().unwrap().1 {
-            MainThreadScriptMsg::Common(script_msg) => script_msg,
-            _ => panic!("unexpected main thread event message!")
-        }
-    }
-}
-
-/// Encapsulates internal communication of shared messages within the script task.
-#[derive(JSTraceable)]
-pub struct SendableMainThreadScriptChan(pub Sender<CommonScriptMsg>);
-
-impl ScriptChan for SendableMainThreadScriptChan {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let SendableMainThreadScriptChan(ref chan) = *self;
-        chan.send(msg).map_err(|_| ())
-    }
-
-    fn clone(&self) -> Box<ScriptChan + Send> {
-        let SendableMainThreadScriptChan(ref chan) = *self;
-        box SendableMainThreadScriptChan((*chan).clone())
-    }
-}
-
-impl SendableMainThreadScriptChan {
-    /// Creates a new script chan.
-    pub fn new() -> (Receiver<CommonScriptMsg>, Box<SendableMainThreadScriptChan>) {
-        let (chan, port) = channel();
-        (port, box SendableMainThreadScriptChan(chan))
-    }
-}
-
-/// Encapsulates internal communication of main thread messages within the script task.
-#[derive(JSTraceable)]
-pub struct MainThreadScriptChan(pub Sender<MainThreadScriptMsg>);
-
-impl ScriptChan for MainThreadScriptChan {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let MainThreadScriptChan(ref chan) = *self;
-        chan.send(MainThreadScriptMsg::Common(msg)).map_err(|_| ())
-    }
-
-    fn clone(&self) -> Box<ScriptChan + Send> {
-        let MainThreadScriptChan(ref chan) = *self;
-        box MainThreadScriptChan((*chan).clone())
-    }
-}
-
-impl MainThreadScriptChan {
-    /// Creates a new script chan.
-    pub fn new() -> (Receiver<MainThreadScriptMsg>, Box<MainThreadScriptChan>) {
-        let (chan, port) = channel();
-        (port, box MainThreadScriptChan(chan))
-    }
-}
-
-// FIXME: Use a task source specific message instead of MainThreadScriptMsg
-#[derive(JSTraceable)]
-pub struct DOMManipulationTaskSource(pub Sender<MainThreadScriptMsg>);
-
-impl ScriptChan for DOMManipulationTaskSource {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let DOMManipulationTaskSource(ref chan) = *self;
-        chan.send(MainThreadScriptMsg::Common(msg)).map_err(|_| ())
-    }
-
-    fn clone(&self) -> Box<ScriptChan + Send> {
-        let DOMManipulationTaskSource(ref chan) = *self;
-        box DOMManipulationTaskSource((*chan).clone())
-    }
-}
-
-// FIXME: Use a task source specific message instead of MainThreadScriptMsg
-#[derive(JSTraceable)]
-pub struct UserInteractionTaskSource(pub Sender<MainThreadScriptMsg>);
-
-impl ScriptChan for UserInteractionTaskSource {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let UserInteractionTaskSource(ref chan) = *self;
-        chan.send(MainThreadScriptMsg::Common(msg)).map_err(|_| ())
-    }
-
-    fn clone(&self) -> Box<ScriptChan + Send> {
-        let UserInteractionTaskSource(ref chan) = *self;
-        box UserInteractionTaskSource((*chan).clone())
-    }
-}
-
-// FIXME: Use a task source specific message instead of MainThreadScriptMsg
-#[derive(JSTraceable)]
-pub struct NetworkingTaskSource(pub Sender<MainThreadScriptMsg>);
-
-impl ScriptChan for NetworkingTaskSource {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let NetworkingTaskSource(ref chan) = *self;
-        chan.send(MainThreadScriptMsg::Common(msg)).map_err(|_| ())
-    }
-
-    fn clone(&self) -> Box<ScriptChan + Send> {
-        let NetworkingTaskSource(ref chan) = *self;
-        box NetworkingTaskSource((*chan).clone())
-    }
-}
-
-// FIXME: Use a task source specific message instead of MainThreadScriptMsg
-#[derive(JSTraceable)]
-pub struct HistoryTraversalTaskSource(pub Sender<MainThreadScriptMsg>);
-
-impl ScriptChan for HistoryTraversalTaskSource {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let HistoryTraversalTaskSource(ref chan) = *self;
-        chan.send(MainThreadScriptMsg::Common(msg)).map_err(|_| ())
-    }
-
-    fn clone(&self) -> Box<ScriptChan + Send> {
-        let HistoryTraversalTaskSource(ref chan) = *self;
-        box HistoryTraversalTaskSource((*chan).clone())
-    }
-}
-
-// FIXME: Use a task source specific message instead of MainThreadScriptMsg
-#[derive(JSTraceable)]
-pub struct FileReadingTaskSource(pub Sender<MainThreadScriptMsg>);
-
-impl ScriptChan for FileReadingTaskSource {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let FileReadingTaskSource(ref chan) = *self;
-        chan.send(MainThreadScriptMsg::Common(msg)).map_err(|_| ())
-    }
-
-    fn clone(&self) -> Box<ScriptChan + Send> {
-        let FileReadingTaskSource(ref chan) = *self;
-        box FileReadingTaskSource((*chan).clone())
-    }
-}
-
-// FIXME: Use a task source specific message instead of MainThreadScriptMsg
-#[derive(JSTraceable)]
-pub struct ProfilerTaskSource(pub Sender<MainThreadScriptMsg>);
-
-impl ScriptChan for ProfilerTaskSource {
-    fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
-        let ProfilerTaskSource(ref chan) = *self;
-        chan.send(MainThreadScriptMsg::Common(msg)).map_err(|_| ())
-    }
-
-    fn clone(&self) -> Box<ScriptChan + Send> {
-        let ProfilerTaskSource(ref chan) = *self;
-        box ProfilerTaskSource((*chan).clone())
-    }
-}
-
-pub struct StackRootTLS<'a>(PhantomData<&'a u32>);
-
-impl<'a> StackRootTLS<'a> {
-    pub fn new(roots: &'a RootCollection) -> StackRootTLS<'a> {
-        STACK_ROOTS.with(|ref r| {
-            r.set(Some(RootCollectionPtr(roots as *const _)))
-        });
-        StackRootTLS(PhantomData)
-    }
-}
-
-impl<'a> Drop for StackRootTLS<'a> {
-    fn drop(&mut self) {
-        STACK_ROOTS.with(|ref r| r.set(None));
-    }
-}
-
-
-/// Information for an entire page. Pages are top-level browsing contexts and can contain multiple
-/// frames.
-#[derive(JSTraceable)]
-// ScriptTask instances are rooted on creation, so this is okay
-#[allow(unrooted_must_root)]
-pub struct ScriptTask {
-    /// A handle to the information pertaining to page layout
-    page: DOMRefCell<Option<Rc<Page>>>,
-    /// A list of data pertaining to loads that have not yet received a network response
-    incomplete_loads: DOMRefCell<Vec<InProgressLoad>>,
-    /// A handle to the image cache task.
-    image_cache_task: ImageCacheTask,
-    /// A handle to the resource task. This is an `Arc` to avoid running out of file descriptors if
-    /// there are many iframes.
-    resource_task: Arc<ResourceTask>,
-    /// A handle to the storage task.
-    storage_task: StorageTask,
-
-    /// The port on which the script task receives messages (load URL, exit, etc.)
-    port: Receiver<MainThreadScriptMsg>,
-    /// A channel to hand out to script task-based entities that need to be able to enqueue
-    /// events in the event queue.
-    chan: MainThreadScriptChan,
-    dom_manipulation_task_source: DOMManipulationTaskSource,
-
-    user_interaction_task_source: UserInteractionTaskSource,
-
-    networking_task_source: NetworkingTaskSource,
-
-    history_traversal_task_source: HistoryTraversalTaskSource,
-
-    file_reading_task_source: FileReadingTaskSource,
-
-    /// A channel to hand out to tasks that need to respond to a message from the script task.
-    control_chan: IpcSender<ConstellationControlMsg>,
-
-    /// The port on which the constellation and layout tasks can communicate with the
-    /// script task.
-    control_port: Receiver<ConstellationControlMsg>,
-
-    /// For communicating load url messages to the constellation
-    constellation_chan: ConstellationChan<ConstellationMsg>,
-
-    /// For communicating layout messages to the constellation
-    layout_to_constellation_chan: ConstellationChan<LayoutMsg>,
-
-    /// A handle to the compositor for communicating ready state messages.
-    compositor: DOMRefCell<IpcSender<ScriptToCompositorMsg>>,
-
-    /// The port on which we receive messages from the image cache
-    image_cache_port: Receiver<ImageCacheResult>,
-
-    /// The channel on which the image cache can send messages to ourself.
-    image_cache_channel: ImageCacheChan,
-
-    /// For providing contact with the time profiler.
-    time_profiler_chan: time::ProfilerChan,
-
-    /// For providing contact with the memory profiler.
-    mem_profiler_chan: mem::ProfilerChan,
-
-    /// For providing instructions to an optional devtools server.
-    devtools_chan: Option<IpcSender<ScriptToDevtoolsControlMsg>>,
-    /// For receiving commands from an optional devtools server. Will be ignored if
-    /// no such server exists.
-    devtools_port: Receiver<DevtoolScriptControlMsg>,
-    devtools_sender: IpcSender<DevtoolScriptControlMsg>,
-
-    /// The JavaScript runtime.
-    js_runtime: Rc<Runtime>,
-
-    mouse_over_targets: DOMRefCell<Vec<JS<Element>>>,
-
-    /// List of pipelines that have been owned and closed by this script task.
-    closed_pipelines: DOMRefCell<HashSet<PipelineId>>,
-
-    scheduler_chan: IpcSender<TimerEventRequest>,
-    timer_event_chan: Sender<TimerEvent>,
-    timer_event_port: Receiver<TimerEvent>,
-
-    content_process_shutdown_chan: IpcSender<()>,
-}
-
-/// In the event of task failure, all data on the stack runs its destructor. However, there
-/// are no reachable, owning pointers to the DOM memory, so it never gets freed by default
-/// when the script task fails. The ScriptMemoryFailsafe uses the destructor bomb pattern
-/// to forcibly tear down the JS compartments for pages associated with the failing ScriptTask.
-struct ScriptMemoryFailsafe<'a> {
-    owner: Option<&'a ScriptTask>,
-}
-
-impl<'a> ScriptMemoryFailsafe<'a> {
-    fn neuter(&mut self) {
-        self.owner = None;
-    }
-
-    fn new(owner: &'a ScriptTask) -> ScriptMemoryFailsafe<'a> {
-        ScriptMemoryFailsafe {
-            owner: Some(owner),
-        }
-    }
-}
-
-impl<'a> Drop for ScriptMemoryFailsafe<'a> {
-    #[allow(unrooted_must_root)]
-    fn drop(&mut self) {
-        match self.owner {
-            Some(owner) => {
-                unsafe {
-                    let page = owner.page.borrow_for_script_deallocation();
-                    for page in page.iter() {
-                        let window = page.window();
-                        window.clear_js_runtime_for_script_deallocation();
-                    }
-                }
-            }
-            None => (),
-        }
-    }
-}
-
-impl ScriptTaskFactory for ScriptTask {
-    fn create_layout_channel(_phantom: Option<&mut ScriptTask>) -> OpaqueScriptLayoutChannel {
-        let (chan, port) = channel();
-        ScriptLayoutChan::new(chan, port)
-    }
-
-    fn clone_layout_channel(_phantom: Option<&mut ScriptTask>, pair: &OpaqueScriptLayoutChannel)
-                            -> Box<Any + Send> {
-        box pair.sender() as Box<Any + Send>
-    }
-
-    fn create(_phantom: Option<&mut ScriptTask>,
-              state: InitialScriptState,
-              layout_chan: &OpaqueScriptLayoutChannel,
-              load_data: LoadData) {
-        let ConstellationChan(const_chan) = state.constellation_chan.clone();
-        let (script_chan, script_port) = channel();
-        let layout_chan = LayoutChan(layout_chan.sender());
-        let failure_info = state.failure_info;
-        task::spawn_named_with_send_on_failure(format!("ScriptTask {:?}", state.id),
-                                               task_state::SCRIPT,
-                                               move || {
-            PipelineNamespace::install(state.pipeline_namespace_id);
-            let roots = RootCollection::new();
-            let _stack_roots_tls = StackRootTLS::new(&roots);
-            let chan = MainThreadScriptChan(script_chan.clone());
-            let channel_for_reporter = chan.clone();
-            let id = state.id;
-            let parent_info = state.parent_info;
-            let mem_profiler_chan = state.mem_profiler_chan.clone();
-            let window_size = state.window_size;
-            let script_task = ScriptTask::new(state,
-                                              script_port,
-                                              script_chan);
-
-            SCRIPT_TASK_ROOT.with(|root| {
-                *root.borrow_mut() = Some(&script_task as *const _);
-            });
-
-            let mut failsafe = ScriptMemoryFailsafe::new(&script_task);
-
-            let new_load = InProgressLoad::new(id, parent_info, layout_chan, window_size,
-                                               load_data.url.clone());
-            script_task.start_page_load(new_load, load_data);
-
-            let reporter_name = format!("script-reporter-{}", id);
-            mem_profiler_chan.run_with_memory_reporting(|| {
-                script_task.start();
-                let _ = script_task.content_process_shutdown_chan.send(());
-            }, reporter_name, channel_for_reporter, CommonScriptMsg::CollectReports);
-
-            // This must always be the very last operation performed before the task completes
-            failsafe.neuter();
-        }, ConstellationMsg::Failure(failure_info), const_chan);
-    }
-}
-
-thread_local!(static GC_CYCLE_START: Cell<Option<Tm>> = Cell::new(None));
-thread_local!(static GC_SLICE_START: Cell<Option<Tm>> = Cell::new(None));
-
-unsafe extern "C" fn gc_slice_callback(_rt: *mut JSRuntime, progress: GCProgress, desc: *const GCDescription) {
-    match progress {
-        GCProgress::GC_CYCLE_BEGIN => {
-            GC_CYCLE_START.with(|start| {
-                start.set(Some(now()));
-                println!("GC cycle began");
-            })
-        },
-        GCProgress::GC_SLICE_BEGIN => {
-            GC_SLICE_START.with(|start| {
-                start.set(Some(now()));
-                println!("GC slice began");
-            })
-        },
-        GCProgress::GC_SLICE_END => {
-            GC_SLICE_START.with(|start| {
-                let dur = now() - start.get().unwrap();
-                start.set(None);
-                println!("GC slice ended: duration={}", dur);
-            })
-        },
-        GCProgress::GC_CYCLE_END => {
-            GC_CYCLE_START.with(|start| {
-                let dur = now() - start.get().unwrap();
-                start.set(None);
-                println!("GC cycle ended: duration={}", dur);
-            })
-        },
-    };
-    if !desc.is_null() {
-        let desc: &GCDescription = &*desc;
-        let invocationKind = match desc.invocationKind_ {
-            JSGCInvocationKind::GC_NORMAL => "GC_NORMAL",
-            JSGCInvocationKind::GC_SHRINK => "GC_SHRINK",
-        };
-        println!("  isCompartment={}, invocationKind={}", desc.isCompartment_, invocationKind);
-    }
-    let _ = stdout().flush();
-}
-
-unsafe extern "C" fn debug_gc_callback(_rt: *mut JSRuntime, status: JSGCStatus, _data: *mut libc::c_void) {
-    match status {
-        JSGCStatus::JSGC_BEGIN => task_state::enter(task_state::IN_GC),
-        JSGCStatus::JSGC_END   => task_state::exit(task_state::IN_GC),
-    }
-}
-
-pub unsafe extern "C" fn shadow_check_callback(_cx: *mut JSContext,
-    _object: HandleObject, _id: HandleId) -> DOMProxyShadowsResult {
-    // XXX implement me
-    DOMProxyShadowsResult::ShadowCheckFailed
-}
-
-#[derive(JSTraceable, HeapSizeOf)]
-pub struct CSSError {
-    filename: String,
-    line: usize,
-    column: usize,
-    msg: String
-}
-
-impl ScriptTask {
-    pub fn page_fetch_complete(id: PipelineId, subpage: Option<SubpageId>, metadata: Metadata)
-                               -> Option<ParserRoot> {
-        SCRIPT_TASK_ROOT.with(|root| {
-            let script_task = unsafe { &*root.borrow().unwrap() };
-            script_task.handle_page_fetch_complete(id, subpage, metadata)
-        })
-    }
-
-    pub fn parsing_complete(id: PipelineId) {
-        SCRIPT_TASK_ROOT.with(|root| {
-            let script_task = unsafe { &*root.borrow().unwrap() };
-            script_task.handle_parsing_complete(id);
-        });
-    }
-
-    pub fn process_event(msg: CommonScriptMsg) {
-        SCRIPT_TASK_ROOT.with(|root| {
-            if let Some(script_task) = *root.borrow() {
-                let script_task = unsafe { &*script_task };
-                script_task.handle_msg_from_script(MainThreadScriptMsg::Common(msg));
-            }
-        });
-    }
-
-    /// Creates a new script task.
-    pub fn new(state: InitialScriptState,
-               port: Receiver<MainThreadScriptMsg>,
-               chan: Sender<MainThreadScriptMsg>)
-               -> ScriptTask {
-        let runtime = ScriptTask::new_rt_and_cx();
-
-        unsafe {
-            JS_SetWrapObjectCallbacks(runtime.rt(),
-                                      &WRAP_CALLBACKS);
-        }
-
-        // Ask the router to proxy IPC messages from the devtools to us.
-        let (ipc_devtools_sender, ipc_devtools_receiver) = ipc::channel().unwrap();
-        let devtools_port = ROUTER.route_ipc_receiver_to_new_mpsc_receiver(ipc_devtools_receiver);
-
-        // Ask the router to proxy IPC messages from the image cache task to us.
-        let (ipc_image_cache_channel, ipc_image_cache_port) = ipc::channel().unwrap();
-        let image_cache_port =
-            ROUTER.route_ipc_receiver_to_new_mpsc_receiver(ipc_image_cache_port);
-
-        let (timer_event_chan, timer_event_port) = channel();
-
-        // Ask the router to proxy IPC messages from the control port to us.
-        let control_port = ROUTER.route_ipc_receiver_to_new_mpsc_receiver(state.control_port);
-
-        ScriptTask {
-            page: DOMRefCell::new(None),
-            incomplete_loads: DOMRefCell::new(vec!()),
-
-            image_cache_task: state.image_cache_task,
-            image_cache_channel: ImageCacheChan(ipc_image_cache_channel),
-            image_cache_port: image_cache_port,
-
-            resource_task: Arc::new(state.resource_task),
-            storage_task: state.storage_task,
-
-            port: port,
-            chan: MainThreadScriptChan(chan.clone()),
-            dom_manipulation_task_source: DOMManipulationTaskSource(chan.clone()),
-            user_interaction_task_source: UserInteractionTaskSource(chan.clone()),
-            networking_task_source: NetworkingTaskSource(chan.clone()),
-            history_traversal_task_source: HistoryTraversalTaskSource(chan.clone()),
-            file_reading_task_source: FileReadingTaskSource(chan),
-
-            control_chan: state.control_chan,
-            control_port: control_port,
-            constellation_chan: state.constellation_chan,
-            layout_to_constellation_chan: state.layout_to_constellation_chan,
-            compositor: DOMRefCell::new(state.compositor),
-            time_profiler_chan: state.time_profiler_chan,
-            mem_profiler_chan: state.mem_profiler_chan,
-
-            devtools_chan: state.devtools_chan,
-            devtools_port: devtools_port,
-            devtools_sender: ipc_devtools_sender,
-
-            js_runtime: Rc::new(runtime),
-            mouse_over_targets: DOMRefCell::new(vec!()),
-            closed_pipelines: DOMRefCell::new(HashSet::new()),
-
-            scheduler_chan: state.scheduler_chan,
-            timer_event_chan: timer_event_chan,
-            timer_event_port: timer_event_port,
-
-            content_process_shutdown_chan: state.content_process_shutdown_chan,
-        }
-    }
-
-    pub fn new_rt_and_cx() -> Runtime {
-        LiveDOMReferences::initialize();
-        let runtime = Runtime::new();
-
-        unsafe {
-            JS_AddExtraGCRootsTracer(runtime.rt(), Some(trace_rust_roots), ptr::null_mut());
-            JS_AddExtraGCRootsTracer(runtime.rt(), Some(trace_refcounted_objects), ptr::null_mut());
-        }
-
-        // Needed for debug assertions about whether GC is running.
-        if cfg!(debug_assertions) {
-            unsafe {
-                JS_SetGCCallback(runtime.rt(), Some(debug_gc_callback), ptr::null_mut());
-            }
-        }
-        if opts::get().gc_profile {
-            unsafe {
-                SetGCSliceCallback(runtime.rt(), Some(gc_slice_callback));
-            }
-        }
-
-        unsafe {
-            unsafe extern "C" fn empty_wrapper_callback(_: *mut JSContext, _: *mut JSObject) -> bool { true }
-            SetDOMCallbacks(runtime.rt(), &DOM_CALLBACKS);
-            SetPreserveWrapperCallback(runtime.rt(), Some(empty_wrapper_callback));
-            // Pre barriers aren't working correctly at the moment
-            DisableIncrementalGC(runtime.rt());
-        }
-
-        runtime
-    }
-
-    // Return the root page in the frame tree. Panics if it doesn't exist.
-    pub fn root_page(&self) -> Rc<Page> {
-        self.page.borrow().as_ref().unwrap().clone()
-    }
-
-    /// Find a child page of the root page by pipeline id. Returns `None` if the root page does
-    /// not exist or the subpage cannot be found.
-    fn find_subpage(&self, pipeline_id: PipelineId) -> Option<Rc<Page>> {
-        self.page.borrow().as_ref().and_then(|page| page.find(pipeline_id))
-    }
-
-    pub fn get_cx(&self) -> *mut JSContext {
-        self.js_runtime.cx()
-    }
-
-    /// Starts the script task. After calling this method, the script task will loop receiving
-    /// messages on its port.
-    pub fn start(&self) {
-        while self.handle_msgs() {
-            // Go on...
-        }
-    }
-
-    /// Handle incoming control messages.
-    fn handle_msgs(&self) -> bool {
-        use self::MixedMessage::{FromScript, FromConstellation, FromScheduler, FromDevtools, FromImageCache};
-
-        // Handle pending resize events.
-        // Gather them first to avoid a double mut borrow on self.
-        let mut resizes = vec!();
-
-        {
-            let page = self.page.borrow();
-            if let Some(page) = page.as_ref() {
-                for page in page.iter() {
-                    // Only process a resize if layout is idle.
-                    let window = page.window();
-                    let resize_event = window.steal_resize_event();
-                    match resize_event {
-                        Some(size) => resizes.push((window.pipeline(), size)),
-                        None => ()
-                    }
-                }
-            }
-        }
-
-        for (id, size) in resizes {
-            self.handle_event(id, ResizeEvent(size));
-        }
-
-        // Store new resizes, and gather all other events.
-        let mut sequential = vec!();
-
-        // Receive at least one message so we don't spinloop.
-        let mut event = {
-            let sel = Select::new();
-            let mut script_port = sel.handle(&self.port);
-            let mut control_port = sel.handle(&self.control_port);
-            let mut timer_event_port = sel.handle(&self.timer_event_port);
-            let mut devtools_port = sel.handle(&self.devtools_port);
-            let mut image_cache_port = sel.handle(&self.image_cache_port);
-            unsafe {
-                script_port.add();
-                control_port.add();
-                timer_event_port.add();
-                if self.devtools_chan.is_some() {
-                    devtools_port.add();
-                }
-                image_cache_port.add();
-            }
-            let ret = sel.wait();
-            if ret == script_port.id() {
-                FromScript(self.port.recv().unwrap())
-            } else if ret == control_port.id() {
-                FromConstellation(self.control_port.recv().unwrap())
-            } else if ret == timer_event_port.id() {
-                FromScheduler(self.timer_event_port.recv().unwrap())
-            } else if ret == devtools_port.id() {
-                FromDevtools(self.devtools_port.recv().unwrap())
-            } else if ret == image_cache_port.id() {
-                FromImageCache(self.image_cache_port.recv().unwrap())
-            } else {
-                panic!("unexpected select result")
-            }
-        };
-
-        // Squash any pending resize, reflow, animation tick, and mouse-move events in the queue.
-        let mut mouse_move_event_index = None;
-        let mut animation_ticks = HashSet::new();
-        loop {
-            match event {
-                // This has to be handled before the ResizeMsg below,
-                // otherwise the page may not have been added to the
-                // child list yet, causing the find() to fail.
-                FromConstellation(ConstellationControlMsg::AttachLayout(
-                        new_layout_info)) => {
-                    self.profile_event(ScriptTaskEventCategory::AttachLayout, || {
-                        self.handle_new_layout(new_layout_info);
-                    })
-                }
-                FromConstellation(ConstellationControlMsg::Resize(id, size)) => {
-                    self.profile_event(ScriptTaskEventCategory::Resize, || {
-                        self.handle_resize(id, size);
-                    })
-                }
-                FromConstellation(ConstellationControlMsg::Viewport(id, rect)) => {
-                    self.profile_event(ScriptTaskEventCategory::SetViewport, || {
-                        self.handle_viewport(id, rect);
-                    })
-                }
-                FromConstellation(ConstellationControlMsg::TickAllAnimations(
-                        pipeline_id)) => {
-                    if !animation_ticks.contains(&pipeline_id) {
-                        animation_ticks.insert(pipeline_id);
-                        sequential.push(event);
-                    }
-                }
-                FromConstellation(ConstellationControlMsg::SendEvent(
-                        _,
-                        MouseMoveEvent(_))) => {
-                    match mouse_move_event_index {
-                        None => {
-                            mouse_move_event_index = Some(sequential.len());
-                            sequential.push(event);
-                        }
-                        Some(index) => {
-                            sequential[index] = event
-                        }
-                    }
-                }
-                _ => {
-                    sequential.push(event);
-                }
-            }
-
-            // If any of our input sources has an event pending, we'll perform another iteration
-            // and check for more resize events. If there are no events pending, we'll move
-            // on and execute the sequential non-resize events we've seen.
-            match self.control_port.try_recv() {
-                Err(_) => match self.port.try_recv() {
-                    Err(_) => match self.timer_event_port.try_recv() {
-                        Err(_) => match self.devtools_port.try_recv() {
-                            Err(_) => match self.image_cache_port.try_recv() {
-                                Err(_) => break,
-                                Ok(ev) => event = FromImageCache(ev),
-                            },
-                            Ok(ev) => event = FromDevtools(ev),
-                        },
-                        Ok(ev) => event = FromScheduler(ev),
-                    },
-                    Ok(ev) => event = FromScript(ev),
-                },
-                Ok(ev) => event = FromConstellation(ev),
-            }
-        }
-
-        // Process the gathered events.
-        for msg in sequential {
-            let category = self.categorize_msg(&msg);
-
-            let result = self.profile_event(category, move || {
-                match msg {
-                    FromConstellation(ConstellationControlMsg::ExitPipeline(id)) => {
-                        if self.handle_exit_pipeline_msg(id) {
-                            return Some(false)
-                        }
-                    },
-                    FromConstellation(inner_msg) => self.handle_msg_from_constellation(inner_msg),
-                    FromScript(inner_msg) => self.handle_msg_from_script(inner_msg),
-                    FromScheduler(inner_msg) => self.handle_timer_event(inner_msg),
-                    FromDevtools(inner_msg) => self.handle_msg_from_devtools(inner_msg),
-                    FromImageCache(inner_msg) => self.handle_msg_from_image_cache(inner_msg),
-                }
-
-                None
-            });
-
-            if let Some(retval) = result {
-                return retval
-            }
-        }
-
-        // Issue batched reflows on any pages that require it (e.g. if images loaded)
-        // TODO(gw): In the future we could probably batch other types of reflows
-        // into this loop too, but for now it's only images.
-        let page = self.page.borrow();
-        if let Some(page) = page.as_ref() {
-            for page in page.iter() {
-                let window = page.window();
-                let pending_reflows = window.get_pending_reflow_count();
-                if pending_reflows > 0 {
-                    window.reflow(ReflowGoal::ForDisplay,
-                                  ReflowQueryType::NoQuery,
-                                  ReflowReason::ImageLoaded);
-                }
-            }
-        }
-
-        true
-    }
-
-    fn categorize_msg(&self, msg: &MixedMessage) -> ScriptTaskEventCategory {
-        match *msg {
-            MixedMessage::FromConstellation(ref inner_msg) => {
-                match *inner_msg {
-                    ConstellationControlMsg::SendEvent(_, _) =>
-                        ScriptTaskEventCategory::DomEvent,
-                    _ => ScriptTaskEventCategory::ConstellationMsg
-                }
-            },
-            MixedMessage::FromDevtools(_) => ScriptTaskEventCategory::DevtoolsMsg,
-            MixedMessage::FromImageCache(_) => ScriptTaskEventCategory::ImageCacheMsg,
-            MixedMessage::FromScript(ref inner_msg) => {
-                match *inner_msg {
-                    MainThreadScriptMsg::Common(CommonScriptMsg::RunnableMsg(ref category, _)) =>
-                        *category,
-                    _ => ScriptTaskEventCategory::ScriptEvent
-                }
-            },
-            MixedMessage::FromScheduler(_) => ScriptTaskEventCategory::TimerEvent,
-        }
-    }
-
-    fn profile_event<F, R>(&self, category: ScriptTaskEventCategory, f: F) -> R
-        where F: FnOnce() -> R {
-
-        if opts::get().profile_script_events {
-            let profiler_cat = match category {
-                ScriptTaskEventCategory::AttachLayout => ProfilerCategory::ScriptAttachLayout,
-                ScriptTaskEventCategory::ConstellationMsg => ProfilerCategory::ScriptConstellationMsg,
-                ScriptTaskEventCategory::DevtoolsMsg => ProfilerCategory::ScriptDevtoolsMsg,
-                ScriptTaskEventCategory::DocumentEvent => ProfilerCategory::ScriptDocumentEvent,
-                ScriptTaskEventCategory::DomEvent => ProfilerCategory::ScriptDomEvent,
-                ScriptTaskEventCategory::FileRead => ProfilerCategory::ScriptFileRead,
-                ScriptTaskEventCategory::ImageCacheMsg => ProfilerCategory::ScriptImageCacheMsg,
-                ScriptTaskEventCategory::InputEvent => ProfilerCategory::ScriptInputEvent,
-                ScriptTaskEventCategory::NetworkEvent => ProfilerCategory::ScriptNetworkEvent,
-                ScriptTaskEventCategory::Resize => ProfilerCategory::ScriptResize,
-                ScriptTaskEventCategory::ScriptEvent => ProfilerCategory::ScriptEvent,
-                ScriptTaskEventCategory::UpdateReplacedElement => {
-                    ProfilerCategory::ScriptUpdateReplacedElement
-                }
-                ScriptTaskEventCategory::StylesheetLoad => ProfilerCategory::ScriptStylesheetLoad,
-                ScriptTaskEventCategory::SetViewport => ProfilerCategory::ScriptSetViewport,
-                ScriptTaskEventCategory::TimerEvent => ProfilerCategory::ScriptTimerEvent,
-                ScriptTaskEventCategory::WebSocketEvent => ProfilerCategory::ScriptWebSocketEvent,
-                ScriptTaskEventCategory::WorkerEvent => ProfilerCategory::ScriptWorkerEvent,
-            };
-            profile(profiler_cat, None, self.time_profiler_chan.clone(), f)
-        } else {
-            f()
-        }
-    }
-
-    fn handle_msg_from_constellation(&self, msg: ConstellationControlMsg) {
-        match msg {
-            ConstellationControlMsg::AttachLayout(_) =>
-                panic!("should have handled AttachLayout already"),
-            ConstellationControlMsg::Navigate(pipeline_id, subpage_id, load_data) =>
-                self.handle_navigate(pipeline_id, Some(subpage_id), load_data),
-            ConstellationControlMsg::SendEvent(id, event) =>
-                self.handle_event(id, event),
-            ConstellationControlMsg::ResizeInactive(id, new_size) =>
-                self.handle_resize_inactive_msg(id, new_size),
-            ConstellationControlMsg::Viewport(..) =>
-                panic!("should have handled Viewport already"),
-            ConstellationControlMsg::Resize(..) =>
-                panic!("should have handled Resize already"),
-            ConstellationControlMsg::ExitPipeline(..) =>
-                panic!("should have handled ExitPipeline already"),
-            ConstellationControlMsg::GetTitle(pipeline_id) =>
-                self.handle_get_title_msg(pipeline_id),
-            ConstellationControlMsg::Freeze(pipeline_id) =>
-                self.handle_freeze_msg(pipeline_id),
-            ConstellationControlMsg::Thaw(pipeline_id) =>
-                self.handle_thaw_msg(pipeline_id),
-            ConstellationControlMsg::MozBrowserEvent(parent_pipeline_id,
-                                                     subpage_id,
-                                                     event) =>
-                self.handle_mozbrowser_event_msg(parent_pipeline_id,
-                                                 subpage_id,
-                                                 event),
-            ConstellationControlMsg::UpdateSubpageId(containing_pipeline_id,
-                                                     old_subpage_id,
-                                                     new_subpage_id) =>
-                self.handle_update_subpage_id(containing_pipeline_id, old_subpage_id, new_subpage_id),
-            ConstellationControlMsg::FocusIFrame(containing_pipeline_id, subpage_id) =>
-                self.handle_focus_iframe_msg(containing_pipeline_id, subpage_id),
-            ConstellationControlMsg::WebDriverScriptCommand(pipeline_id, msg) =>
-                self.handle_webdriver_msg(pipeline_id, msg),
-            ConstellationControlMsg::TickAllAnimations(pipeline_id) =>
-                self.handle_tick_all_animations(pipeline_id),
-            ConstellationControlMsg::WebFontLoaded(pipeline_id) =>
-                self.handle_web_font_loaded(pipeline_id),
-            ConstellationControlMsg::DispatchFrameLoadEvent {
-                target: pipeline_id, parent: containing_id } =>
-                self.handle_frame_load_event(containing_id, pipeline_id),
-            ConstellationControlMsg::ReportCSSError(pipeline_id, filename, line, column, msg) =>
-                self.handle_css_error_reporting(pipeline_id, filename, line, column, msg),
-        }
-    }
-
-    fn handle_msg_from_script(&self, msg: MainThreadScriptMsg) {
-        match msg {
-            MainThreadScriptMsg::Navigate(id, load_data) =>
-                self.handle_navigate(id, None, load_data),
-            MainThreadScriptMsg::ExitWindow(id) =>
-                self.handle_exit_window_msg(id),
-            MainThreadScriptMsg::MainThreadRunnableMsg(runnable) =>
-                runnable.handler(self),
-            MainThreadScriptMsg::DocumentLoadsComplete(id) =>
-                self.handle_loads_complete(id),
-            MainThreadScriptMsg::Common(CommonScriptMsg::RunnableMsg(_, runnable)) => {
-                // The category of the runnable is ignored by the pattern, however
-                // it is still respected by profiling (see categorize_msg).
-                if !runnable.is_cancelled() {
-                    runnable.handler()
-                }
-            }
-            MainThreadScriptMsg::Common(CommonScriptMsg::RefcountCleanup(addr)) =>
-                LiveDOMReferences::cleanup(addr),
-            MainThreadScriptMsg::Common(CommonScriptMsg::CollectReports(reports_chan)) =>
-                self.collect_reports(reports_chan),
-        }
-    }
-
-    fn handle_timer_event(&self, timer_event: TimerEvent) {
-        let TimerEvent(source, id) = timer_event;
-
-        let pipeline_id = match source {
-            TimerSource::FromWindow(pipeline_id) => pipeline_id,
-            TimerSource::FromWorker => panic!("Worker timeouts must not be sent to script task"),
-        };
-
-        let page = self.root_page();
-        let page = page.find(pipeline_id).expect("ScriptTask: received fire timer msg for a
-            pipeline ID not associated with this script task. This is a bug.");
-        let window = page.window();
-
-        window.handle_fire_timer(id);
-    }
-
-    fn handle_msg_from_devtools(&self, msg: DevtoolScriptControlMsg) {
-        let page = self.root_page();
-        match msg {
-            DevtoolScriptControlMsg::EvaluateJS(id, s, reply) => {
-                let window = get_page(&page, id).window();
-                let global_ref = GlobalRef::Window(window.r());
-                devtools::handle_evaluate_js(&global_ref, s, reply)
-            },
-            DevtoolScriptControlMsg::GetRootNode(id, reply) =>
-                devtools::handle_get_root_node(&page, id, reply),
-            DevtoolScriptControlMsg::GetDocumentElement(id, reply) =>
-                devtools::handle_get_document_element(&page, id, reply),
-            DevtoolScriptControlMsg::GetChildren(id, node_id, reply) =>
-                devtools::handle_get_children(&page, id, node_id, reply),
-            DevtoolScriptControlMsg::GetLayout(id, node_id, reply) =>
-                devtools::handle_get_layout(&page, id, node_id, reply),
-            DevtoolScriptControlMsg::GetCachedMessages(pipeline_id, message_types, reply) =>
-                devtools::handle_get_cached_messages(pipeline_id, message_types, reply),
-            DevtoolScriptControlMsg::ModifyAttribute(id, node_id, modifications) =>
-                devtools::handle_modify_attribute(&page, id, node_id, modifications),
-            DevtoolScriptControlMsg::WantsLiveNotifications(id, to_send) => {
-                let window = get_page(&page, id).window();
-                let global_ref = GlobalRef::Window(window.r());
-                devtools::handle_wants_live_notifications(&global_ref, to_send)
-            },
-            DevtoolScriptControlMsg::SetTimelineMarkers(_pipeline_id, marker_types, reply) =>
-                devtools::handle_set_timeline_markers(&page, marker_types, reply),
-            DevtoolScriptControlMsg::DropTimelineMarkers(_pipeline_id, marker_types) =>
-                devtools::handle_drop_timeline_markers(&page, marker_types),
-            DevtoolScriptControlMsg::RequestAnimationFrame(pipeline_id, name) =>
-                devtools::handle_request_animation_frame(&page, pipeline_id, name),
-        }
-    }
-
-    fn handle_msg_from_image_cache(&self, msg: ImageCacheResult) {
-        msg.responder.unwrap().respond(msg.image_response);
-    }
-
-    fn handle_webdriver_msg(&self, pipeline_id: PipelineId, msg: WebDriverScriptCommand) {
-        let page = self.root_page();
-        match msg {
-            WebDriverScriptCommand::ExecuteScript(script, reply) =>
-                webdriver_handlers::handle_execute_script(&page, pipeline_id, script, reply),
-            WebDriverScriptCommand::FindElementCSS(selector, reply) =>
-                webdriver_handlers::handle_find_element_css(&page, pipeline_id, selector, reply),
-            WebDriverScriptCommand::FindElementsCSS(selector, reply) =>
-                webdriver_handlers::handle_find_elements_css(&page, pipeline_id, selector, reply),
-            WebDriverScriptCommand::FocusElement(element_id, reply) =>
-                webdriver_handlers::handle_focus_element(&page, pipeline_id, element_id, reply),
-            WebDriverScriptCommand::GetActiveElement(reply) =>
-                webdriver_handlers::handle_get_active_element(&page, pipeline_id, reply),
-            WebDriverScriptCommand::GetElementTagName(node_id, reply) =>
-                webdriver_handlers::handle_get_name(&page, pipeline_id, node_id, reply),
-            WebDriverScriptCommand::GetElementAttribute(node_id, name, reply) =>
-                webdriver_handlers::handle_get_attribute(&page, pipeline_id, node_id, name, reply),
-            WebDriverScriptCommand::GetElementCSS(node_id, name, reply) =>
-                webdriver_handlers::handle_get_css(&page, pipeline_id, node_id, name, reply),
-            WebDriverScriptCommand::GetElementText(node_id, reply) =>
-                webdriver_handlers::handle_get_text(&page, pipeline_id, node_id, reply),
-            WebDriverScriptCommand::GetFrameId(frame_id, reply) =>
-                webdriver_handlers::handle_get_frame_id(&page, pipeline_id, frame_id, reply),
-            WebDriverScriptCommand::GetUrl(reply) =>
-                webdriver_handlers::handle_get_url(&page, pipeline_id, reply),
-            WebDriverScriptCommand::GetWindowSize(reply) =>
-                webdriver_handlers::handle_get_window_size(&page, pipeline_id, reply),
-            WebDriverScriptCommand::IsEnabled(element_id, reply) =>
-                webdriver_handlers::handle_is_enabled(&page, pipeline_id, element_id, reply),
-            WebDriverScriptCommand::IsSelected(element_id, reply) =>
-                webdriver_handlers::handle_is_selected(&page, pipeline_id, element_id, reply),
-            WebDriverScriptCommand::GetTitle(reply) =>
-                webdriver_handlers::handle_get_title(&page, pipeline_id, reply),
-            WebDriverScriptCommand::ExecuteAsyncScript(script, reply) =>
-                webdriver_handlers::handle_execute_async_script(&page, pipeline_id, script, reply),
-        }
-    }
-
-    fn handle_resize(&self, id: PipelineId, size: WindowSizeData) {
-        if let Some(ref page) = self.find_subpage(id) {
-            let window = page.window();
-            window.set_resize_event(size);
-            return;
-        }
-        let mut loads = self.incomplete_loads.borrow_mut();
-        if let Some(ref mut load) = loads.iter_mut().find(|load| load.pipeline_id == id) {
-            load.window_size = Some(size);
-            return;
-        }
-        panic!("resize sent to nonexistent pipeline");
-    }
-
-    fn handle_viewport(&self, id: PipelineId, rect: Rect<f32>) {
-        let page = self.page.borrow();
-        if let Some(page) = page.as_ref() {
-            if let Some(ref inner_page) = page.find(id) {
-                let window = inner_page.window();
-                if window.set_page_clip_rect_with_new_viewport(rect) {
-                    let page = get_page(page, id);
-                    self.rebuild_and_force_reflow(&*page, ReflowReason::Viewport);
-                }
-                return;
-            }
-        }
-        let mut loads = self.incomplete_loads.borrow_mut();
-        if let Some(ref mut load) = loads.iter_mut().find(|load| load.pipeline_id == id) {
-            load.clip_rect = Some(rect);
-            return;
-        }
-        panic!("Page rect message sent to nonexistent pipeline");
-    }
-
-    fn handle_new_layout(&self, new_layout_info: NewLayoutInfo) {
-        let NewLayoutInfo {
-            containing_pipeline_id,
-            new_pipeline_id,
-            subpage_id,
-            load_data,
-            paint_chan,
-            failure,
-            pipeline_port,
-            layout_shutdown_chan,
-            content_process_shutdown_chan,
-        } = new_layout_info;
-
-        let layout_pair = ScriptTask::create_layout_channel(None::<&mut ScriptTask>);
-        let layout_chan = LayoutChan(*ScriptTask::clone_layout_channel(
-            None::<&mut ScriptTask>,
-            &layout_pair).downcast::<Sender<layout_interface::Msg>>().unwrap());
-
-        let layout_creation_info = NewLayoutTaskInfo {
-            id: new_pipeline_id,
-            url: load_data.url.clone(),
-            is_parent: false,
-            layout_pair: layout_pair,
-            pipeline_port: pipeline_port,
-            constellation_chan: self.layout_to_constellation_chan.clone(),
-            failure: failure,
-            paint_chan: paint_chan,
-            script_chan: self.control_chan.clone(),
-            image_cache_task: self.image_cache_task.clone(),
-            layout_shutdown_chan: layout_shutdown_chan,
-            content_process_shutdown_chan: content_process_shutdown_chan,
-        };
-
-        let page = self.root_page();
-        let parent_page = page.find(containing_pipeline_id).expect("ScriptTask: received a layout
-            whose parent has a PipelineId which does not correspond to a pipeline in the script
-            task's page tree. This is a bug.");
-        let parent_window = parent_page.window();
-
-        // Tell layout to actually spawn the task.
-        parent_window.layout_chan()
-                     .0
-                     .send(layout_interface::Msg::CreateLayoutTask(layout_creation_info))
-                     .unwrap();
-
-        // Kick off the fetch for the new resource.
-        let new_load = InProgressLoad::new(new_pipeline_id, Some((containing_pipeline_id, subpage_id)),
-                                           layout_chan, parent_window.window_size(),
-                                           load_data.url.clone());
-        self.start_page_load(new_load, load_data);
-    }
-
-    fn handle_loads_complete(&self, pipeline: PipelineId) {
-        let page = get_page(&self.root_page(), pipeline);
-        let doc = page.document();
-        let doc = doc.r();
-        if doc.loader().is_blocked() {
-            return;
-        }
-
-        doc.mut_loader().inhibit_events();
-
-        // https://html.spec.whatwg.org/multipage/#the-end step 7
-        let addr: Trusted<Document> = Trusted::new(doc, self.chan.clone());
-        let handler = box DocumentProgressHandler::new(addr.clone());
-        self.chan.send(CommonScriptMsg::RunnableMsg(ScriptTaskEventCategory::DocumentEvent, handler)).unwrap();
-
-        let ConstellationChan(ref chan) = self.constellation_chan;
-        chan.send(ConstellationMsg::LoadComplete(pipeline)).unwrap();
-    }
-
-    pub fn get_reports(cx: *mut JSContext, path_seg: String) -> Vec<Report> {
-        let mut reports = vec![];
-
-        unsafe {
-            let rt = JS_GetRuntime(cx);
-            let mut stats = ::std::mem::zeroed();
-            if CollectServoSizes(rt, &mut stats) {
-                let mut report = |mut path_suffix, kind, size| {
-                    let mut path = path![path_seg, "js"];
-                    path.append(&mut path_suffix);
-                    reports.push(Report {
-                        path: path,
-                        kind: kind,
-                        size: size as usize,
-                    })
-                };
-
-                // A note about possibly confusing terminology: the JS GC "heap" is allocated via
-                // mmap/VirtualAlloc, which means it's not on the malloc "heap", so we use
-                // `ExplicitNonHeapSize` as its kind.
-
-                report(path!["gc-heap", "used"],
-                       ReportKind::ExplicitNonHeapSize,
-                       stats.gcHeapUsed);
-
-                report(path!["gc-heap", "unused"],
-                       ReportKind::ExplicitNonHeapSize,
-                       stats.gcHeapUnused);
-
-                report(path!["gc-heap", "admin"],
-                       ReportKind::ExplicitNonHeapSize,
-                       stats.gcHeapAdmin);
-
-                report(path!["gc-heap", "decommitted"],
-                       ReportKind::ExplicitNonHeapSize,
-                       stats.gcHeapDecommitted);
-
-                // SpiderMonkey uses the system heap, not jemalloc.
-                report(path!["malloc-heap"],
-                       ReportKind::ExplicitSystemHeapSize,
-                       stats.mallocHeap);
-
-                report(path!["non-heap"],
-                       ReportKind::ExplicitNonHeapSize,
-                       stats.nonHeap);
-            }
-        }
-        reports
-    }
-
-    fn collect_reports(&self, reports_chan: ReportsChan) {
-        let mut urls = vec![];
-        let mut dom_tree_size = 0;
-        let mut reports = vec![];
-
-        if let Some(root_page) = self.page.borrow().as_ref() {
-            for it_page in root_page.iter() {
-                let current_url = it_page.document().url().serialize();
-                urls.push(current_url.clone());
-
-                for child in it_page.document().upcast::<Node>().traverse_preorder() {
-                    dom_tree_size += heap_size_of_self_and_children(&*child);
-                }
-                let window = it_page.window();
-                dom_tree_size += heap_size_of_self_and_children(&*window);
-
-                reports.push(Report {
-                    path: path![format!("url({})", current_url), "dom-tree"],
-                    kind: ReportKind::ExplicitJemallocHeapSize,
-                    size: dom_tree_size,
-                })
-            }
-        }
-        let path_seg = format!("url({})", urls.join(", "));
-        reports.extend(ScriptTask::get_reports(self.get_cx(), path_seg));
-        reports_chan.send(reports);
-    }
-
-    /// Handles freeze message
-    fn handle_freeze_msg(&self, id: PipelineId) {
-        if let Some(root_page) = self.page.borrow().as_ref() {
-            if let Some(ref inner_page) = root_page.find(id) {
-                let window = inner_page.window();
-                window.freeze();
-                return;
-            }
-        }
-        let mut loads = self.incomplete_loads.borrow_mut();
-        if let Some(ref mut load) = loads.iter_mut().find(|load| load.pipeline_id == id) {
-            load.is_frozen = true;
-            return;
-        }
-        panic!("freeze sent to nonexistent pipeline");
-    }
-
-    /// Handles thaw message
-    fn handle_thaw_msg(&self, id: PipelineId) {
-        if let Some(ref inner_page) = self.root_page().find(id) {
-            let needed_reflow = inner_page.set_reflow_status(false);
-            if needed_reflow {
-                self.rebuild_and_force_reflow(&*inner_page, ReflowReason::CachedPageNeededReflow);
-            }
-            let window = inner_page.window();
-            window.thaw();
-            return;
-        }
-        let mut loads = self.incomplete_loads.borrow_mut();
-        if let Some(ref mut load) = loads.iter_mut().find(|load| load.pipeline_id == id) {
-            load.is_frozen = false;
-            return;
-        }
-        panic!("thaw sent to nonexistent pipeline");
-    }
-
-    fn handle_focus_iframe_msg(&self,
-                               parent_pipeline_id: PipelineId,
-                               subpage_id: SubpageId) {
-        let borrowed_page = self.root_page();
-        let page = borrowed_page.find(parent_pipeline_id).unwrap();
-
-        let doc = page.document();
-        let frame_element = doc.find_iframe(subpage_id);
-
-        if let Some(ref frame_element) = frame_element {
-            doc.begin_focus_transaction();
-            doc.request_focus(frame_element.upcast());
-            doc.commit_focus_transaction(FocusType::Parent);
-        }
-    }
-
-    /// Handles a mozbrowser event, for example see:
-    /// https://developer.mozilla.org/en-US/docs/Web/Events/mozbrowserloadstart
-    fn handle_mozbrowser_event_msg(&self,
-                                   parent_pipeline_id: PipelineId,
-                                   subpage_id: SubpageId,
-                                   event: MozBrowserEvent) {
-        let borrowed_page = self.root_page();
-
-        let frame_element = borrowed_page.find(parent_pipeline_id).and_then(|page| {
-            let doc = page.document();
-            doc.find_iframe(subpage_id)
-        });
-
-        if let Some(ref frame_element) = frame_element {
-            frame_element.dispatch_mozbrowser_event(event);
-        }
-    }
-
-    fn handle_update_subpage_id(&self,
-                                containing_pipeline_id: PipelineId,
-                                old_subpage_id: SubpageId,
-                                new_subpage_id: SubpageId) {
-        let borrowed_page = self.root_page();
-
-        let frame_element = borrowed_page.find(containing_pipeline_id).and_then(|page| {
-            let doc = page.document();
-            doc.find_iframe(old_subpage_id)
-        });
-
-        frame_element.unwrap().update_subpage_id(new_subpage_id);
-    }
-
-    /// Window was resized, but this script was not active, so don't reflow yet
-    fn handle_resize_inactive_msg(&self, id: PipelineId, new_size: WindowSizeData) {
-        let page = self.root_page();
-        let page = page.find(id).expect("Received resize message for PipelineId not associated
-            with a page in the page tree. This is a bug.");
-        let window = page.window();
-        window.set_window_size(new_size);
-        page.set_reflow_status(true);
-    }
-
-    /// We have gotten a window.close from script, which we pass on to the compositor.
-    /// We do not shut down the script task now, because the compositor will ask the
-    /// constellation to shut down the pipeline, which will clean everything up
-    /// normally. If we do exit, we will tear down the DOM nodes, possibly at a point
-    /// where layout is still accessing them.
-    fn handle_exit_window_msg(&self, _: PipelineId) {
-        debug!("script task handling exit window msg");
-
-        // TODO(tkuehn): currently there is only one window,
-        // so this can afford to be naive and just shut down the
-        // compositor. In the future it'll need to be smarter.
-        self.compositor.borrow_mut().send(ScriptToCompositorMsg::Exit).unwrap();
-    }
-
-    /// We have received notification that the response associated with a load has completed.
-    /// Kick off the document and frame tree creation process using the result.
-    fn handle_page_fetch_complete(&self, id: PipelineId, subpage: Option<SubpageId>,
-                                  metadata: Metadata) -> Option<ParserRoot> {
-        let idx = self.incomplete_loads.borrow().iter().position(|load| {
-            load.pipeline_id == id && load.parent_info.map(|info| info.1) == subpage
-        });
-        // The matching in progress load structure may not exist if
-        // the pipeline exited before the page load completed.
-        match idx {
-            Some(idx) => {
-                let load = self.incomplete_loads.borrow_mut().remove(idx);
-                Some(self.load(metadata, load))
-            }
-            None => {
-                assert!(self.closed_pipelines.borrow().contains(&id));
-                None
-            }
-        }
-    }
-
-    /// Handles a request for the window title.
-    fn handle_get_title_msg(&self, pipeline_id: PipelineId) {
-        let page = get_page(&self.root_page(), pipeline_id);
-        let document = page.document();
-        document.send_title_to_compositor();
-    }
-
-    /// Handles a request to exit the script task and shut down layout.
-    /// Returns true if the script task should shut down and false otherwise.
-    fn handle_exit_pipeline_msg(&self, id: PipelineId) -> bool {
-        self.closed_pipelines.borrow_mut().insert(id);
-
-        // Check if the exit message is for an in progress load.
-        let idx = self.incomplete_loads.borrow().iter().position(|load| {
-            load.pipeline_id == id
-        });
-
-        if let Some(idx) = idx {
-            let load = self.incomplete_loads.borrow_mut().remove(idx);
-
-            // Tell the layout task to begin shutting down, and wait until it
-            // processed this message.
-            let (response_chan, response_port) = channel();
-            let LayoutChan(chan) = load.layout_chan;
-            if chan.send(layout_interface::Msg::PrepareToExit(response_chan)).is_ok() {
-                debug!("shutting down layout for page {:?}", id);
-                response_port.recv().unwrap();
-                chan.send(layout_interface::Msg::ExitNow).ok();
-            }
-
-            let has_pending_loads = self.incomplete_loads.borrow().len() > 0;
-            let has_root_page = self.page.borrow().is_some();
-
-            // Exit if no pending loads and no root page
-            return !has_pending_loads && !has_root_page;
-        }
-
-        // If root is being exited, shut down all pages
-        let page = self.root_page();
-        let window = page.window();
-        if window.pipeline() == id {
-            debug!("shutting down layout for root page {:?}", id);
-            shut_down_layout(&page);
-            return true
-        }
-
-        // otherwise find just the matching page and exit all sub-pages
-        if let Some(ref mut child_page) = page.remove(id) {
-            shut_down_layout(&*child_page);
-        }
-        false
-    }
-
-    /// Handles when layout task finishes all animation in one tick
-    fn handle_tick_all_animations(&self, id: PipelineId) {
-        let page = get_page(&self.root_page(), id);
-        let document = page.document();
-        document.run_the_animation_frame_callbacks();
-    }
-
-    /// Handles a Web font being loaded. Does nothing if the page no longer exists.
-    fn handle_web_font_loaded(&self, pipeline_id: PipelineId) {
-        if let Some(ref page) = self.find_subpage(pipeline_id)  {
-            self.rebuild_and_force_reflow(page, ReflowReason::WebFontLoaded);
-        }
-    }
-
-    /// Notify the containing document of a child frame that has completed loading.
-    fn handle_frame_load_event(&self, containing_pipeline: PipelineId, id: PipelineId) {
-        let page = get_page(&self.root_page(), containing_pipeline);
-        let document = page.document();
-        if let Some(iframe) = document.find_iframe_by_pipeline(id) {
-            iframe.iframe_load_event_steps();
-        }
-    }
-
-    /// The entry point to document loading. Defines bindings, sets up the window and document
-    /// objects, parses HTML and CSS, and kicks off initial layout.
-    fn load(&self, metadata: Metadata, incomplete: InProgressLoad) -> ParserRoot {
-        let final_url = metadata.final_url.clone();
-        {
-            // send the final url to the layout task.
-            let LayoutChan(ref chan) = incomplete.layout_chan;
-            chan.send(layout_interface::Msg::SetFinalUrl(final_url.clone())).unwrap();
-
-            // update the pipeline url
-            let ConstellationChan(ref chan) = self.constellation_chan;
-            chan.send(ConstellationMsg::SetFinalUrl(incomplete.pipeline_id, final_url.clone())).unwrap();
-        }
-        debug!("ScriptTask: loading {} on page {:?}", incomplete.url.serialize(), incomplete.pipeline_id);
-
-        // We should either be initializing a root page or loading a child page of an
-        // existing one.
-        let root_page_exists = self.page.borrow().is_some();
-
-        let frame_element = incomplete.parent_info.and_then(|(parent_id, subpage_id)| {
-            // The root page may not exist yet, if the parent of this frame
-            // exists in a different script task.
-            let borrowed_page = self.page.borrow();
-
-            // In the case a parent id exists but the matching page
-            // cannot be found, this means the page exists in a different
-            // script task (due to origin) so it shouldn't be returned.
-            // TODO: window.parent will continue to return self in that
-            // case, which is wrong. We should be returning an object that
-            // denies access to most properties (per
-            // https://github.com/servo/servo/issues/3939#issuecomment-62287025).
-            borrowed_page.as_ref().and_then(|borrowed_page| {
-                borrowed_page.find(parent_id).and_then(|page| {
-                    let doc = page.document();
-                    doc.find_iframe(subpage_id)
-                })
-            })
-        });
-
-        // Create a new frame tree entry.
-        let page = Rc::new(Page::new(incomplete.pipeline_id));
-        if !root_page_exists {
-            // We have a new root frame tree.
-            *self.page.borrow_mut() = Some(page.clone());
-        } else if let Some((parent, _)) = incomplete.parent_info {
-            // We have a new child frame.
-            let parent_page = self.root_page();
-            // TODO(gw): This find will fail when we are sharing script tasks
-            // between cross origin iframes in the same TLD.
-            let parent_page = parent_page.find(parent)
-                                         .expect("received load for subpage with missing parent");
-            parent_page.children.borrow_mut().push(page.clone());
-        }
-
-        enum PageToRemove {
-            Root,
-            Child(PipelineId),
-        }
-        struct AutoPageRemover<'a> {
-            page: PageToRemove,
-            script_task: &'a ScriptTask,
-            neutered: bool,
-        }
-        impl<'a> AutoPageRemover<'a> {
-            fn new(script_task: &'a ScriptTask, page: PageToRemove) -> AutoPageRemover<'a> {
-                AutoPageRemover {
-                    page: page,
-                    script_task: script_task,
-                    neutered: false,
-                }
-            }
-
-            fn neuter(&mut self) {
-                self.neutered = true;
-            }
-        }
-        impl<'a> Drop for AutoPageRemover<'a> {
-            fn drop(&mut self) {
-                if !self.neutered {
-                    match self.page {
-                        PageToRemove::Root => *self.script_task.page.borrow_mut() = None,
-                        PageToRemove::Child(id) => {
-                            self.script_task.root_page().remove(id).unwrap();
-                        }
-                    }
-                }
-            }
-        }
-
-        let page_to_remove = if !root_page_exists {
-            PageToRemove::Root
-        } else {
-            PageToRemove::Child(incomplete.pipeline_id)
-        };
-        let mut page_remover = AutoPageRemover::new(self, page_to_remove);
-        let MainThreadScriptChan(ref sender) = self.chan;
-        let DOMManipulationTaskSource(ref dom_sender) = self.dom_manipulation_task_source;
-        let UserInteractionTaskSource(ref user_sender) = self.user_interaction_task_source;
-        let NetworkingTaskSource(ref network_sender) = self.networking_task_source;
-        let HistoryTraversalTaskSource(ref history_sender) = self.history_traversal_task_source;
-        let FileReadingTaskSource(ref file_sender) = self.file_reading_task_source;
-
-        let (ipc_timer_event_chan, ipc_timer_event_port) = ipc::channel().unwrap();
-        ROUTER.route_ipc_receiver_to_mpsc_sender(ipc_timer_event_port,
-                                                 self.timer_event_chan.clone());
-
-        // Create the window and document objects.
-        let window = Window::new(self.js_runtime.clone(),
-                                 page.clone(),
-                                 MainThreadScriptChan(sender.clone()),
-                                 DOMManipulationTaskSource(dom_sender.clone()),
-                                 UserInteractionTaskSource(user_sender.clone()),
-                                 NetworkingTaskSource(network_sender.clone()),
-                                 HistoryTraversalTaskSource(history_sender.clone()),
-                                 FileReadingTaskSource(file_sender.clone()),
-                                 self.image_cache_channel.clone(),
-                                 self.compositor.borrow_mut().clone(),
-                                 self.image_cache_task.clone(),
-                                 self.resource_task.clone(),
-                                 self.storage_task.clone(),
-                                 self.mem_profiler_chan.clone(),
-                                 self.devtools_chan.clone(),
-                                 self.constellation_chan.clone(),
-                                 self.scheduler_chan.clone(),
-                                 ipc_timer_event_chan,
-                                 incomplete.layout_chan,
-                                 incomplete.pipeline_id,
-                                 incomplete.parent_info,
-                                 incomplete.window_size);
-
-        let last_modified = metadata.headers.as_ref().and_then(|headers| {
-            headers.get().map(|&LastModified(HttpDate(ref tm))| dom_last_modified(tm))
-        });
-
-        let content_type = match metadata.content_type {
-            Some(ContentType(Mime(TopLevel::Text, SubLevel::Xml, _))) => {
-                Some(DOMString::from("text/xml"))
-            }
-
-            Some(ContentType(Mime(TopLevel::Text, SubLevel::Plain, _))) => {
-                Some(DOMString::from("text/plain"))
-            }
-
-            _ => None
-        };
-
-        let loader = DocumentLoader::new_with_task(self.resource_task.clone(),
-                                                   Some(page.pipeline()),
-                                                   Some(incomplete.url.clone()));
-
-        let is_html_document = match metadata.content_type {
-            Some(ContentType(Mime(TopLevel::Text, SubLevel::Xml, _))) =>
-                IsHTMLDocument::NonHTMLDocument,
-            _ => IsHTMLDocument::HTMLDocument,
-        };
-
-        let document = Document::new(window.r(),
-                                     Some(final_url.clone()),
-                                     is_html_document,
-                                     content_type,
-                                     last_modified,
-                                     DocumentSource::FromParser,
-                                     loader);
-
-        let frame_element = frame_element.r().map(Castable::upcast);
-        window.init_browsing_context(document.r(), frame_element);
-
-        document.set_ready_state(DocumentReadyState::Loading);
-
-        // Create the root frame
-        page.set_frame(Some(Frame {
-            document: JS::from_rooted(&document),
-            window: JS::from_rooted(&window),
-        }));
-
-        let ConstellationChan(ref chan) = self.constellation_chan;
-        chan.send(ConstellationMsg::ActivateDocument(incomplete.pipeline_id)).unwrap();
-
-        let is_javascript = incomplete.url.scheme == "javascript";
-        let parse_input = if is_javascript {
-            use url::percent_encoding::percent_decode_to;
-
-            // Turn javascript: URL into JS code to eval, according to the steps in
-            // https://html.spec.whatwg.org/multipage/#javascript-protocol
-            let _ar = JSAutoRequest::new(self.get_cx());
-            let mut script_source_bytes = Vec::new();
-            // Start with the scheme data of the parsed URL (5.), while percent-decoding (8.)
-            percent_decode_to(incomplete.url.non_relative_scheme_data().unwrap().as_bytes(),
-                              &mut script_source_bytes);
-            // Append question mark and query component, if any (6.), while percent-decoding (8.)
-            if let Some(ref query) = incomplete.url.query {
-                script_source_bytes.push(b'?');
-                percent_decode_to(query.as_bytes(), &mut script_source_bytes);
-            }
-            // Append number sign and fragment component if any (7.), while percent-decoding (8.)
-            if let Some(ref fragment) = incomplete.url.fragment {
-                script_source_bytes.push(b'#');
-                percent_decode_to(fragment.as_bytes(), &mut script_source_bytes);
-            }
-
-            // UTF-8 decode (9.)
-            let script_source = String::from_utf8_lossy(&script_source_bytes);
-
-            // Script source is ready to be evaluated (11.)
-            unsafe {
-                let mut jsval = RootedValue::new(self.get_cx(), UndefinedValue());
-                window.evaluate_js_on_global_with_result(&script_source, jsval.handle_mut());
-                let strval = DOMString::from_jsval(self.get_cx(),
-                                                   jsval.handle(),
-                                                   StringificationBehavior::Empty);
-                strval.unwrap_or(DOMString::new())
-            }
-        } else {
-            DOMString::new()
-        };
-
-        match metadata.content_type {
-            Some(ContentType(Mime(TopLevel::Text, SubLevel::Xml, _))) => {
-                parse_xml(document.r(),
-                          parse_input,
-                          final_url,
-                          xml::ParseContext::Owner(Some(incomplete.pipeline_id)));
-            }
-            _ => {
-                parse_html(document.r(),
-                           parse_input,
-                           final_url,
-                           ParseContext::Owner(Some(incomplete.pipeline_id)));
-            }
-        }
-
-        if incomplete.is_frozen {
-            window.freeze();
-        }
-
-        page_remover.neuter();
-
-        document.get_current_parser().unwrap()
-    }
-
-    fn notify_devtools(&self, title: DOMString, url: Url, ids: (PipelineId, Option<WorkerId>)) {
-        if let Some(ref chan) = self.devtools_chan {
-            let page_info = DevtoolsPageInfo {
-                title: String::from(title),
-                url: url,
-            };
-            chan.send(ScriptToDevtoolsControlMsg::NewGlobal(
-                        ids,
-                        self.devtools_sender.clone(),
-                        page_info)).unwrap();
-        }
-    }
-
-    fn scroll_fragment_point(&self, pipeline_id: PipelineId, element: &Element) {
-        // FIXME(#8275, pcwalton): This is pretty bogus when multiple layers are involved.
-        // Really what needs to happen is that this needs to go through layout to ask which
-        // layer the element belongs to, and have it send the scroll message to the
-        // compositor.
-        let rect = element.upcast::<Node>().get_bounding_content_box();
-
-        // In order to align with element edges, we snap to unscaled pixel boundaries, since the
-        // paint task currently does the same for drawing elements. This is important for pages
-        // that require pixel perfect scroll positioning for proper display (like Acid2). Since we
-        // don't have the device pixel ratio here, this might not be accurate, but should work as
-        // long as the ratio is a whole number. Once #8275 is fixed this should actually take into
-        // account the real device pixel ratio.
-        let point = Point2D::new(rect.origin.x.to_nearest_px() as f32,
-                                 rect.origin.y.to_nearest_px() as f32);
-
-        self.compositor.borrow_mut().send(ScriptToCompositorMsg::ScrollFragmentPoint(
-                                                 pipeline_id, LayerId::null(), point, false)).unwrap();
-    }
-
-    /// Reflows non-incrementally, rebuilding the entire layout tree in the process.
-    fn rebuild_and_force_reflow(&self, page: &Page, reason: ReflowReason) {
-        let document = page.document();
-        document.dirty_all_nodes();
-        let window = window_from_node(document.r());
-        window.reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery, reason);
-    }
-
-    /// This is the main entry point for receiving and dispatching DOM events.
-    ///
-    /// TODO: Actually perform DOM event dispatch.
-    fn handle_event(&self, pipeline_id: PipelineId, event: CompositorEvent) {
-
-        match event {
-            ResizeEvent(new_size) => {
-                self.handle_resize_event(pipeline_id, new_size);
-            }
-
-            MouseButtonEvent(event_type, button, point) => {
-                self.handle_mouse_event(pipeline_id, event_type, button, point);
-            }
-
-            MouseMoveEvent(point) => {
-                let page = get_page(&self.root_page(), pipeline_id);
-                let document = page.document();
-
-                let mut prev_mouse_over_targets: RootedVec<JS<Element>> = RootedVec::new();
-                for target in &*self.mouse_over_targets.borrow_mut() {
-                    prev_mouse_over_targets.push(target.clone());
-                }
-
-                // We temporarily steal the list of targets over which the mouse is to pass it to
-                // handle_mouse_move_event() in a safe RootedVec container.
-                let mut mouse_over_targets = RootedVec::new();
-                std_mem::swap(&mut *self.mouse_over_targets.borrow_mut(), &mut *mouse_over_targets);
-                document.handle_mouse_move_event(self.js_runtime.rt(), point, &mut mouse_over_targets);
-
-                // Notify Constellation about anchors that are no longer mouse over targets.
-                for target in &*prev_mouse_over_targets {
-                    if !mouse_over_targets.contains(target) && target.is::<HTMLAnchorElement>() {
-                        let event = ConstellationMsg::NodeStatus(None);
-                        let ConstellationChan(ref chan) = self.constellation_chan;
-                        chan.send(event).unwrap();
-                        break;
-                    }
-                }
-
-                // Notify Constellation about the topmost anchor mouse over target.
-                for target in &*mouse_over_targets {
-                    if target.is::<HTMLAnchorElement>() {
-                        let status = target.get_attribute(&ns!(), &atom!("href"))
-                            .and_then(|href| {
-                                let value = href.value();
-                                let url = document.url();
-                                url.join(&value).map(|url| url.serialize()).ok()
-                            });
-                        let event = ConstellationMsg::NodeStatus(status);
-                        let ConstellationChan(ref chan) = self.constellation_chan;
-                        chan.send(event).unwrap();
-                        break;
-                    }
-                }
-
-                std_mem::swap(&mut *self.mouse_over_targets.borrow_mut(), &mut *mouse_over_targets);
-            }
-
-            TouchEvent(event_type, identifier, point) => {
-                let handled = self.handle_touch_event(pipeline_id, event_type, identifier, point);
-                match event_type {
-                    TouchEventType::Down => {
-                        if handled {
-                            // TODO: Wait to see if preventDefault is called on the first touchmove event.
-                            self.compositor.borrow_mut()
-                                .send(ScriptToCompositorMsg::TouchEventProcessed(
-                                        EventResult::DefaultAllowed)).unwrap();
-                        } else {
-                            self.compositor.borrow_mut()
-                                .send(ScriptToCompositorMsg::TouchEventProcessed(
-                                        EventResult::DefaultPrevented)).unwrap();
-                        }
-                    }
-                    _ => {
-                        // TODO: Calling preventDefault on a touchup event should prevent clicks.
-                    }
-                }
-            }
-
-            KeyEvent(key, state, modifiers) => {
-                let page = get_page(&self.root_page(), pipeline_id);
-                let document = page.document();
-                document.dispatch_key_event(
-                    key, state, modifiers, &mut self.compositor.borrow_mut());
-            }
-        }
-    }
-
-    fn handle_mouse_event(&self,
-                          pipeline_id: PipelineId,
-                          mouse_event_type: MouseEventType,
-                          button: MouseButton,
-                          point: Point2D<f32>) {
-        let page = get_page(&self.root_page(), pipeline_id);
-        let document = page.document();
-        document.handle_mouse_event(self.js_runtime.rt(), button, point, mouse_event_type);
-    }
-
-    fn handle_touch_event(&self,
-                          pipeline_id: PipelineId,
-                          event_type: TouchEventType,
-                          identifier: TouchId,
-                          point: Point2D<f32>)
-                          -> bool {
-        let page = get_page(&self.root_page(), pipeline_id);
-        let document = page.document();
-        document.handle_touch_event(self.js_runtime.rt(), event_type, identifier, point)
-    }
-
-    /// https://html.spec.whatwg.org/multipage/#navigating-across-documents
-    /// The entry point for content to notify that a new load has been requested
-    /// for the given pipeline (specifically the "navigate" algorithm).
-    fn handle_navigate(&self, pipeline_id: PipelineId, subpage_id: Option<SubpageId>, load_data: LoadData) {
-        // Step 8.
-        {
-            let nurl = &load_data.url;
-            if let Some(ref fragment) = nurl.fragment {
-                let page = get_page(&self.root_page(), pipeline_id);
-                let document = page.document();
-                let document = document.r();
-                let url = document.url();
-                if url.scheme == nurl.scheme && url.scheme_data == nurl.scheme_data &&
-                    url.query == nurl.query && load_data.method == Method::Get {
-                    match document.find_fragment_node(&*fragment) {
-                        Some(ref node) => {
-                            self.scroll_fragment_point(pipeline_id, node.r());
-                        }
-                        None => {}
-                    }
-                    return;
-                }
-            }
-        }
-
-        match subpage_id {
-            Some(subpage_id) => {
-                let borrowed_page = self.root_page();
-                let iframe = borrowed_page.find(pipeline_id).and_then(|page| {
-                    let doc = page.document();
-                    doc.find_iframe(subpage_id)
-                });
-                if let Some(iframe) = iframe.r() {
-                    iframe.navigate_or_reload_child_browsing_context(Some(load_data.url));
-                }
-            }
-            None => {
-                let ConstellationChan(ref const_chan) = self.constellation_chan;
-                const_chan.send(ConstellationMsg::LoadUrl(pipeline_id, load_data)).unwrap();
-            }
-        }
-    }
-
-    fn handle_resize_event(&self, pipeline_id: PipelineId, new_size: WindowSizeData) {
-        let page = get_page(&self.root_page(), pipeline_id);
-        let window = page.window();
-        window.set_window_size(new_size);
-        window.force_reflow(ReflowGoal::ForDisplay,
-                            ReflowQueryType::NoQuery,
-                            ReflowReason::WindowResize);
-
-        let document = page.document();
-        let fragment_node = window.steal_fragment_name()
-                                  .and_then(|name| document.find_fragment_node(&*name));
-        match fragment_node {
-            Some(ref node) => self.scroll_fragment_point(pipeline_id, node.r()),
-            None => {}
-        }
-
-        // http://dev.w3.org/csswg/cssom-view/#resizing-viewports
-        // https://dvcs.w3.org/hg/dom3events/raw-file/tip/html/DOM3-Events.html#event-type-resize
-        let uievent = UIEvent::new(window.r(),
-                                   DOMString::from("resize"), EventBubbles::DoesNotBubble,
-                                   EventCancelable::NotCancelable, Some(window.r()),
-                                   0i32);
-        uievent.upcast::<Event>().fire(window.upcast());
-    }
-
-    /// Initiate a non-blocking fetch for a specified resource. Stores the InProgressLoad
-    /// argument until a notification is received that the fetch is complete.
-    fn start_page_load(&self, incomplete: InProgressLoad, mut load_data: LoadData) {
-        let id = incomplete.pipeline_id.clone();
-        let subpage = incomplete.parent_info.clone().map(|p| p.1);
-
-        let script_chan = self.chan.clone();
-        let resource_task = self.resource_task.clone();
-
-        let context = Arc::new(Mutex::new(ParserContext::new(id, subpage, script_chan.clone(),
-                                                             load_data.url.clone())));
-        let (action_sender, action_receiver) = ipc::channel().unwrap();
-        let listener = NetworkListener {
-            context: context,
-            script_chan: script_chan.clone(),
-        };
-        ROUTER.add_route(action_receiver.to_opaque(), box move |message| {
-            listener.notify(message.to().unwrap());
-        });
-        let response_target = AsyncResponseTarget {
-            sender: action_sender,
-        };
-
-        if load_data.url.scheme == "javascript" {
-            load_data.url = url!("about:blank");
-        }
-
-        resource_task.send(ControlMsg::Load(NetLoadData {
-            context: LoadContext::Browsing,
-            url: load_data.url,
-            method: load_data.method,
-            headers: Headers::new(),
-            preserved_headers: load_data.headers,
-            data: load_data.data,
-            cors: None,
-            pipeline_id: Some(id),
-            credentials_flag: true,
-        }, LoadConsumer::Listener(response_target), None)).unwrap();
-
-        self.incomplete_loads.borrow_mut().push(incomplete);
-    }
-
-    fn handle_parsing_complete(&self, id: PipelineId) {
-        let parent_page = self.root_page();
-        let page = match parent_page.find(id) {
-            Some(page) => page,
-            None => return,
-        };
-
-        let document = page.document();
-        let final_url = document.url();
-
-        // https://html.spec.whatwg.org/multipage/#the-end step 1
-        document.set_ready_state(DocumentReadyState::Interactive);
-
-        // TODO: Execute step 2 here.
-
-        // Kick off the initial reflow of the page.
-        debug!("kicking off initial reflow of {:?}", final_url);
-        document.disarm_reflow_timeout();
-        document.content_changed(document.upcast(),
-                                 NodeDamage::OtherNodeDamage);
-        let window = window_from_node(document.r());
-        window.reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery, ReflowReason::FirstLoad);
-
-        // No more reflow required
-        page.set_reflow_status(false);
-
-        // https://html.spec.whatwg.org/multipage/#the-end steps 3-4.
-        document.process_deferred_scripts();
-
-        window.set_fragment_name(final_url.fragment.clone());
-
-        // Notify devtools that a new script global exists.
-        //TODO: should this happen as soon as the global is created, or at least once the first
-        // script runs?
-        self.notify_devtools(document.Title(), (*final_url).clone(), (id, None));
-    }
-
-    fn handle_css_error_reporting(&self, pipeline_id: PipelineId, filename: String,
-                                  line: usize, column: usize, msg: String) {
-        let parent_page = self.root_page();
-        let page = match parent_page.find(pipeline_id) {
-            Some(page) => page,
-            None => return,
-        };
-
-        let document = page.document();
-        let css_error = CSSError {
-            filename: filename,
-            line: line,
-            column: column,
-            msg: msg
-        };
-        document.report_css_error(css_error);
-    }
-}
-
-impl Drop for ScriptTask {
-    fn drop(&mut self) {
-        SCRIPT_TASK_ROOT.with(|root| {
-            *root.borrow_mut() = None;
-        });
-    }
-}
-
-/// Shuts down layout for the given page tree.
-fn shut_down_layout(page_tree: &Rc<Page>) {
-    let mut channels = vec!();
-
-    for page in page_tree.iter() {
-        // Tell the layout task to begin shutting down, and wait until it
-        // processed this message.
-        let (response_chan, response_port) = channel();
-        let window = page.window();
-        let LayoutChan(chan) = window.layout_chan();
-        if chan.send(layout_interface::Msg::PrepareToExit(response_chan)).is_ok() {
-            channels.push(chan);
-            response_port.recv().unwrap();
-        }
-    }
-
-    // Drop our references to the JSContext and DOM objects.
-    for page in page_tree.iter() {
-        let window = page.window();
-        window.clear_js_runtime();
-        // Sever the connection between the global and the DOM tree
-        page.set_frame(None);
-    }
-
-    // Destroy the layout task. If there were node leaks, layout will now crash safely.
-    for chan in channels {
-        chan.send(layout_interface::Msg::ExitNow).ok();
-    }
-}
-
-pub fn get_page(page: &Rc<Page>, pipeline_id: PipelineId) -> Rc<Page> {
-    page.find(pipeline_id).expect("ScriptTask: received an event \
-        message for a layout channel that is not associated with this script task.\
-         This is a bug.")
-}
-
-fn dom_last_modified(tm: &Tm) -> String {
-    tm.to_local().strftime("%m/%d/%Y %H:%M:%S").unwrap().to_string()
-}