Auto merge of #8262 - nxnfufunezn:Remove_JS_root, r=Ms2ger

Removed JS::root #8251

Fixes #8251 

r? @Ms2ger

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25 files changed, 98 insertions, 126 deletions

diff --git a/components/script/dom/bindings/global.rs b/components/script/dom/bindings/global.rs
index a1a1c68c8c0..e91e94a0a4b 100644
--- a/components/script/dom/bindings/global.rs
+++ b/components/script/dom/bindings/global.rs
@@ -230,8 +230,8 @@ impl GlobalField {
     /// Create a stack-bounded root for this reference.
     pub fn root(&self) -> GlobalRoot {
         match *self {
-            GlobalField::Window(ref window) => GlobalRoot::Window(window.root()),
-            GlobalField::Worker(ref worker) => GlobalRoot::Worker(worker.root()),
+            GlobalField::Window(ref window) => GlobalRoot::Window(Root::from_ref(window)),
+            GlobalField::Worker(ref worker) => GlobalRoot::Worker(Root::from_ref(worker)),
         }
     }
 }
diff --git a/components/script/dom/bindings/js.rs b/components/script/dom/bindings/js.rs
index a6af7680a96..c78399189ab 100644
--- a/components/script/dom/bindings/js.rs
+++ b/components/script/dom/bindings/js.rs
@@ -73,10 +73,6 @@ impl<T> JS<T> {
 }
 
 impl<T: Reflectable> JS<T> {
-    /// Root this JS-owned value to prevent its collection as garbage.
-    pub fn root(&self) -> Root<T> {
-        Root::new(self.ptr)
-    }
     /// Create a JS<T> from a Root<T>
     /// XXX Not a great API. Should be a call on Root<T> instead
     #[allow(unrooted_must_root)]
@@ -291,7 +287,7 @@ impl<T: Reflectable> MutHeap<JS<T>> {
     pub fn get(&self) -> Root<T> {
         debug_assert!(task_state::get().is_script());
         unsafe {
-            ptr::read(self.val.get()).root()
+            Root::from_ref(&*ptr::read(self.val.get()))
         }
     }
 }
@@ -369,7 +365,7 @@ impl<T: Reflectable> MutNullableHeap<JS<T>> {
     pub fn get(&self) -> Option<Root<T>> {
         debug_assert!(task_state::get().is_script());
         unsafe {
-            ptr::read(self.ptr.get()).map(|o| o.root())
+            ptr::read(self.ptr.get()).map(|o| Root::from_ref(&*o))
         }
     }
 
diff --git a/components/script/dom/canvasrenderingcontext2d.rs b/components/script/dom/canvasrenderingcontext2d.rs
index aa7936f69f5..a42e98a1a03 100644
--- a/components/script/dom/canvasrenderingcontext2d.rs
+++ b/components/script/dom/canvasrenderingcontext2d.rs
@@ -148,7 +148,7 @@ impl CanvasRenderingContext2D {
     }
 
     fn mark_as_dirty(&self) {
-        self.canvas.root().upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
+        self.canvas.upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
     }
 
     fn update_transform(&self) {
@@ -290,7 +290,7 @@ impl CanvasRenderingContext2D {
         let smoothing_enabled = self.state.borrow().image_smoothing_enabled;
 
         // If the source and target canvas are the same
-        let msg = if self.canvas.root().r() == canvas {
+        let msg = if &*self.canvas == canvas {
             CanvasMsg::Canvas2d(Canvas2dMsg::DrawImageSelf(image_size, dest_rect, source_rect, smoothing_enabled))
         } else { // Source and target canvases are different
             let context = match canvas.get_or_init_2d_context() {
@@ -367,8 +367,7 @@ impl CanvasRenderingContext2D {
 
     #[inline]
     fn request_image_from_cache(&self, url: Url) -> ImageResponse {
-        let canvas = self.canvas.root();
-        let window = window_from_node(canvas.r());
+        let window = window_from_node(&*self.canvas);
         canvas_utils::request_image_from_cache(window.r(), url)
     }
 
@@ -422,7 +421,7 @@ impl LayoutCanvasRenderingContext2DHelpers for LayoutJS<CanvasRenderingContext2D
 impl CanvasRenderingContext2DMethods for CanvasRenderingContext2D {
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-canvas
     fn Canvas(&self) -> Root<HTMLCanvasElement> {
-        self.canvas.root()
+        Root::from_ref(&*self.canvas)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-save
@@ -764,7 +763,7 @@ impl CanvasRenderingContext2DMethods for CanvasRenderingContext2D {
                 StringOrCanvasGradientOrCanvasPattern::eString(result)
             },
             CanvasFillOrStrokeStyle::Gradient(ref gradient) => {
-                StringOrCanvasGradientOrCanvasPattern::eCanvasGradient(gradient.root())
+                StringOrCanvasGradientOrCanvasPattern::eCanvasGradient(Root::from_ref(&*gradient))
             },
         }
     }
@@ -804,7 +803,7 @@ impl CanvasRenderingContext2DMethods for CanvasRenderingContext2D {
                 StringOrCanvasGradientOrCanvasPattern::eString(result)
             },
             CanvasFillOrStrokeStyle::Gradient(ref gradient) => {
-                StringOrCanvasGradientOrCanvasPattern::eCanvasGradient(gradient.root())
+                StringOrCanvasGradientOrCanvasPattern::eCanvasGradient(Root::from_ref(&*gradient))
             },
         }
     }
@@ -881,7 +880,7 @@ impl CanvasRenderingContext2DMethods for CanvasRenderingContext2D {
         let (sender, receiver) = ipc::channel::<Vec<u8>>().unwrap();
         let dest_rect = Rect::new(Point2D::new(sx.to_i32().unwrap(), sy.to_i32().unwrap()),
                                   Size2D::new(sw as i32, sh as i32));
-        let canvas_size = self.canvas.root().r().get_size();
+        let canvas_size = self.canvas.get_size();
         let canvas_size = Size2D::new(canvas_size.width as f64, canvas_size.height as f64);
         self.ipc_renderer
             .send(CanvasMsg::Canvas2d(Canvas2dMsg::GetImageData(dest_rect, canvas_size, sender)))
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 0a94f9f5504..4559bb0981c 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -391,8 +391,7 @@ impl Document {
             None => false,
             Some(elements) => {
                 let position = elements.iter()
-                                       .map(|elem| elem.root())
-                                       .position(|element| element.r() == to_unregister)
+                                       .position(|element| &**element == to_unregister)
                                        .expect("This element should be in registered.");
                 elements.remove(position);
                 elements.is_empty()
@@ -428,7 +427,7 @@ impl Document {
                 let root = root.upcast::<Node>();
                 for node in root.traverse_preorder() {
                     if let Some(elem) = node.downcast() {
-                        if (*elements)[head].root().r() == elem {
+                        if &*(*elements)[head] == elem {
                             head += 1;
                         }
                         if new_node == node.r() || head == elements.len() {
@@ -685,8 +684,7 @@ impl Document {
         // under the mouse.
         for target in prev_mouse_over_targets.iter() {
             if !mouse_over_targets.contains(target) {
-                let target = target.root();
-                let target_ref = target.r();
+                let target_ref = &**target;
                 if target_ref.get_hover_state() {
                     target_ref.set_hover_state(false);
 
@@ -749,27 +747,27 @@ impl Document {
             },
         };
         let target = el.upcast::<EventTarget>();
-        let window = self.window.root();
+        let window = &*self.window;
 
         let client_x = Finite::wrap(point.x as f64);
         let client_y = Finite::wrap(point.y as f64);
         let page_x = Finite::wrap(point.x as f64 + window.PageXOffset() as f64);
         let page_y = Finite::wrap(point.y as f64 + window.PageYOffset() as f64);
 
-        let touch = Touch::new(window.r(), identifier, target,
+        let touch = Touch::new(window, identifier, target,
                                client_x, client_y, // TODO: Get real screen coordinates?
                                client_x, client_y,
                                page_x, page_y);
 
         let mut touches = RootedVec::new();
         touches.push(JS::from_rooted(&touch));
-        let touches = TouchList::new(window.r(), touches.r());
+        let touches = TouchList::new(window, touches.r());
 
-        let event = TouchEvent::new(window.r(),
+        let event = TouchEvent::new(window,
                                     event_name,
                                     EventBubbles::Bubbles,
                                     EventCancelable::Cancelable,
-                                    Some(window.r()),
+                                    Some(window),
                                     0i32,
                                     &touches, &touches, &touches,
                                     // FIXME: modifier keys
@@ -777,9 +775,9 @@ impl Document {
         let event = event.upcast::<Event>();
         let result = event.fire(target);
 
-        window.r().reflow(ReflowGoal::ForDisplay,
-                          ReflowQueryType::NoQuery,
-                          ReflowReason::MouseEvent);
+        window.reflow(ReflowGoal::ForDisplay,
+                      ReflowQueryType::NoQuery,
+                      ReflowReason::MouseEvent);
         result
     }
 
@@ -1089,13 +1087,15 @@ impl Document {
         }
         let mut deferred_scripts = self.deferred_scripts.borrow_mut();
         while !deferred_scripts.is_empty() {
-            let script = deferred_scripts[0].root();
-            // Part of substep 1.
-            if !script.is_ready_to_be_executed() {
-                return;
+            {
+                let script = &*deferred_scripts[0];
+                // Part of substep 1.
+                if !script.is_ready_to_be_executed() {
+                    return;
+                }
+                // Substep 2.
+                script.execute();
             }
-            // Substep 2.
-            script.execute();
             // Substep 3.
             deferred_scripts.remove(0);
             // Substep 4 (implicit).
@@ -1110,7 +1110,7 @@ impl Document {
         // Execute the first in-order asap-executed script if it's ready, repeat as required.
         // Re-borrowing the list for each step because it can also be borrowed under execute.
         while self.asap_in_order_scripts_list.borrow().len() > 0 {
-            let script = self.asap_in_order_scripts_list.borrow()[0].root();
+            let script = Root::from_ref(&*self.asap_in_order_scripts_list.borrow()[0]);
             if !script.r().is_ready_to_be_executed() {
                 break;
             }
@@ -1121,7 +1121,7 @@ impl Document {
         let mut idx = 0;
         // Re-borrowing the set for each step because it can also be borrowed under execute.
         while idx < self.asap_scripts_set.borrow().len() {
-            let script = self.asap_scripts_set.borrow()[idx].root();
+            let script = Root::from_ref(&*self.asap_scripts_set.borrow()[idx]);
             if !script.r().is_ready_to_be_executed() {
                 idx += 1;
                 continue;
@@ -1332,7 +1332,7 @@ impl Document {
     }
 
     pub fn get_element_by_id(&self, id: &Atom) -> Option<Root<Element>> {
-        self.idmap.borrow().get(&id).map(|ref elements| (*elements)[0].root())
+        self.idmap.borrow().get(&id).map(|ref elements| Root::from_ref(&*(*elements)[0]))
     }
 
     pub fn record_element_state_change(&self, el: &Element, which: ElementState) {
@@ -1925,7 +1925,7 @@ impl DocumentMethods for Document {
 
     // https://html.spec.whatwg.org/multipage/#dom-document-defaultview
     fn DefaultView(&self) -> Root<Window> {
-        self.window.root()
+        Root::from_ref(&*self.window)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-document-cookie
diff --git a/components/script/dom/domrectlist.rs b/components/script/dom/domrectlist.rs
index cd67dbc28c7..963d97df623 100644
--- a/components/script/dom/domrectlist.rs
+++ b/components/script/dom/domrectlist.rs
@@ -42,7 +42,7 @@ impl DOMRectListMethods for DOMRectList {
     fn Item(&self, index: u32) -> Option<Root<DOMRect>> {
         let rects = &self.rects;
         if index < rects.len() as u32 {
-            Some(rects[index as usize].root())
+            Some(Root::from_ref(&*rects[index as usize]))
         } else {
             None
         }
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index 46628935bb1..eaee0d241f0 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -874,16 +874,15 @@ impl Element {
     }
 
     pub fn get_attribute(&self, namespace: &Namespace, local_name: &Atom) -> Option<Root<Attr>> {
-        self.attrs.borrow().iter().map(JS::root).find(|attr| {
+        self.attrs.borrow().iter().find(|attr| {
             attr.local_name() == local_name && attr.namespace() == namespace
-        })
+        }).map(|js| Root::from_ref(&**js))
     }
 
     // https://dom.spec.whatwg.org/#concept-element-attributes-get-by-name
     pub fn get_attribute_by_name(&self, name: DOMString) -> Option<Root<Attr>> {
         let name = &self.parsed_name(name);
-        self.attrs.borrow().iter().map(JS::root)
-             .find(|a| a.r().name() == name)
+        self.attrs.borrow().iter().find(|a| a.name() == name).map(|js| Root::from_ref(&**js))
     }
 
     pub fn set_attribute_from_parser(&self,
@@ -891,8 +890,8 @@ impl Element {
                                      value: DOMString,
                                      prefix: Option<Atom>) {
         // Don't set if the attribute already exists, so we can handle add_attrs_if_missing
-        if self.attrs.borrow().iter().map(JS::root)
-                .any(|a| *a.r().local_name() == qname.local && *a.r().namespace() == qname.ns) {
+        if self.attrs.borrow().iter()
+                .any(|a| *a.local_name() == qname.local && *a.namespace() == qname.ns) {
             return;
         }
 
@@ -942,7 +941,8 @@ impl Element {
                                        find: F)
                                        where F: Fn(&Attr)
                                        -> bool {
-        let attr = self.attrs.borrow().iter().map(JS::root).find(|attr| find(&attr));
+        let attr = self.attrs.borrow().iter()
+            .find(|attr| find(&attr)).map(|js| Root::from_ref(&**js));
         if let Some(attr) = attr {
             attr.set_value(value, self);
         } else {
@@ -973,10 +973,10 @@ impl Element {
     fn remove_first_matching_attribute<F>(&self, find: F) -> Option<Root<Attr>>
         where F: Fn(&Attr) -> bool
     {
-        let idx = self.attrs.borrow().iter().map(JS::root).position(|attr| find(&attr));
+        let idx = self.attrs.borrow().iter().position(|attr| find(&attr));
 
         idx.map(|idx| {
-            let attr = (*self.attrs.borrow())[idx].root();
+            let attr = Root::from_ref(&*(*self.attrs.borrow())[idx]);
             self.attrs.borrow_mut().remove(idx);
             attr.set_owner(None);
             if attr.namespace() == &ns!("") {
@@ -1005,8 +1005,8 @@ impl Element {
 
     pub fn has_attribute(&self, local_name: &Atom) -> bool {
         assert!(local_name.bytes().all(|b| b.to_ascii_lowercase() == b));
-        self.attrs.borrow().iter().map(JS::root).any(|attr| {
-            attr.r().local_name() == local_name && attr.r().namespace() == &ns!("")
+        self.attrs.borrow().iter().any(|attr| {
+            attr.local_name() == local_name && attr.namespace() == &ns!("")
         })
     }
 
@@ -1695,8 +1695,8 @@ impl<'a> ::selectors::Element for Root<Element> {
                     })
             },
             NamespaceConstraint::Any => {
-                self.attrs.borrow().iter().map(JS::root).any(|attr| {
-                     attr.local_name() == local_name && test(&attr.value())
+                self.attrs.borrow().iter().any(|attr| {
+                    attr.local_name() == local_name && test(&attr.value())
                 })
             }
         }
diff --git a/components/script/dom/filelist.rs b/components/script/dom/filelist.rs
index d695ac8f43a..78a9ee30012 100644
--- a/components/script/dom/filelist.rs
+++ b/components/script/dom/filelist.rs
@@ -40,7 +40,7 @@ impl FileListMethods for FileList {
 
     // https://w3c.github.io/FileAPI/#dfn-item
     fn Item(&self, index: u32) -> Option<Root<File>> {
-        Some(self.list[index as usize].root())
+        Some(Root::from_ref(&*(self.list[index as usize])))
     }
 
     // check-tidy: no specs after this line
diff --git a/components/script/dom/formdata.rs b/components/script/dom/formdata.rs
index a51e058b864..5956aadd26c 100644
--- a/components/script/dom/formdata.rs
+++ b/components/script/dom/formdata.rs
@@ -90,7 +90,7 @@ impl FormDataMethods for FormData {
                  .get(&name)
                  .map(|entry| match entry[0] {
                      FormDatum::StringData(ref s) => eString(s.clone()),
-                     FormDatum::FileData(ref f) => eFile(f.root()),
+                     FormDatum::FileData(ref f) => eFile(Root::from_ref(&*f)),
                  })
     }
 
diff --git a/components/script/dom/htmlcanvaselement.rs b/components/script/dom/htmlcanvaselement.rs
index 47126ed3dd0..67894f36429 100644
--- a/components/script/dom/htmlcanvaselement.rs
+++ b/components/script/dom/htmlcanvaselement.rs
@@ -153,7 +153,7 @@ impl HTMLCanvasElement {
         }
 
         match *self.context.borrow().as_ref().unwrap() {
-            CanvasContext::Context2d(ref context) => Some(context.root()),
+            CanvasContext::Context2d(ref context) => Some(Root::from_ref(&*context)),
             _   => None,
         }
     }
@@ -182,7 +182,7 @@ impl HTMLCanvasElement {
         }
 
         if let Some(CanvasContext::WebGL(ref context)) = *self.context.borrow() {
-            Some(context.root())
+            Some(Root::from_ref(&*context))
         } else {
             None
         }
diff --git a/components/script/dom/htmlcollection.rs b/components/script/dom/htmlcollection.rs
index 4ddc0fef6dd..62335a33a6e 100644
--- a/components/script/dom/htmlcollection.rs
+++ b/components/script/dom/htmlcollection.rs
@@ -164,7 +164,7 @@ impl HTMLCollection {
 
     pub fn elements_iter(&self) -> HTMLCollectionElementsIter {
         let ref filter = self.collection.1;
-        let root = self.collection.0.root();
+        let root = Root::from_ref(&*self.collection.0);
         let mut node_iter = root.traverse_preorder();
         let _ = node_iter.next();  // skip the root node
         HTMLCollectionElementsIter {
diff --git a/components/script/dom/htmlelement.rs b/components/script/dom/htmlelement.rs
index bb52cbc2402..6ebf0106099 100644
--- a/components/script/dom/htmlelement.rs
+++ b/components/script/dom/htmlelement.rs
@@ -360,8 +360,8 @@ impl HTMLElement {
 
     pub fn supported_prop_names_custom_attr(&self) -> Vec<DOMString> {
         let element = self.upcast::<Element>();
-        element.attrs().iter().map(JS::root).filter_map(|attr| {
-            let raw_name = attr.r().local_name();
+        element.attrs().iter().filter_map(|attr| {
+            let raw_name = attr.local_name();
             to_camel_case(&raw_name)
         }).collect()
     }
diff --git a/components/script/dom/htmlscriptelement.rs b/components/script/dom/htmlscriptelement.rs
index 118c0648e77..4f1b0ca135a 100644
--- a/components/script/dom/htmlscriptelement.rs
+++ b/components/script/dom/htmlscriptelement.rs
@@ -364,7 +364,7 @@ impl HTMLScriptElement {
 
         // Step 1.
         let doc = document_from_node(self);
-        if self.parser_inserted.get() && doc.r() != self.parser_document.root().r() {
+        if self.parser_inserted.get() && &*doc != &*self.parser_document {
             return;
         }
 
diff --git a/components/script/dom/namednodemap.rs b/components/script/dom/namednodemap.rs
index 5c78de0ed51..fc344e78ccf 100644
--- a/components/script/dom/namednodemap.rs
+++ b/components/script/dom/namednodemap.rs
@@ -42,7 +42,7 @@ impl NamedNodeMapMethods for NamedNodeMap {
 
     // https://dom.spec.whatwg.org/#dom-namednodemap-item
     fn Item(&self, index: u32) -> Option<Root<Attr>> {
-        self.owner.attrs().get(index as usize).map(JS::root)
+        self.owner.attrs().get(index as usize).map(|js| Root::from_ref(&**js))
     }
 
     // https://dom.spec.whatwg.org/#dom-namednodemap-getnameditem
@@ -87,7 +87,7 @@ impl NamedNodeMapMethods for NamedNodeMap {
 
     // https://heycam.github.io/webidl/#dfn-supported-property-names
     fn SupportedPropertyNames(&self) -> Vec<DOMString> {
-        self.owner.attrs().iter().map(JS::root).map(|attr| {
+        self.owner.attrs().iter().map(|attr| {
             (**attr.name()).to_owned()
         }).collect()
     }
diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index c5a891d56db..a8dd8972ca0 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -1648,7 +1648,7 @@ impl Node {
                 let node_elem = node.downcast::<Element>().unwrap();
                 let copy_elem = copy.downcast::<Element>().unwrap();
 
-                for attr in node_elem.attrs().iter().map(JS::root) {
+                for attr in node_elem.attrs().iter() {
                     copy_elem.push_new_attribute(attr.local_name().clone(),
                                                  attr.value().clone(),
                                                  attr.name().clone(),
@@ -1719,12 +1719,10 @@ impl Node {
                 let prefix_atom = prefix.as_ref().map(|s| Atom::from_slice(s));
 
                 // Step 2.
-                let namespace_attr =
-                    element.attrs()
-                           .iter()
-                           .map(|attr| attr.root())
-                           .find(|attr| attr_defines_namespace(attr.r(),
-                                                               &prefix_atom));
+                let attrs = element.attrs();
+                let namespace_attr = attrs.iter().find(|attr| {
+                    attr_defines_namespace(attr, &prefix_atom)
+                });
 
                 // Steps 2.1-2.
                 if let Some(attr) = namespace_attr {
@@ -2154,12 +2152,10 @@ impl NodeMethods for Node {
             // FIXME(https://github.com/rust-lang/rust/issues/23338)
             let attrs = element.attrs();
             attrs.iter().all(|attr| {
-                let attr = attr.root();
                 other_element.attrs().iter().any(|other_attr| {
-                    let other_attr = other_attr.root();
-                    (*attr.r().namespace() == *other_attr.r().namespace()) &&
-                    (attr.r().local_name() == other_attr.r().local_name()) &&
-                    (**attr.r().value() == **other_attr.r().value())
+                    (*attr.namespace() == *other_attr.namespace()) &&
+                    (attr.local_name() == other_attr.local_name()) &&
+                    (**attr.value() == **other_attr.value())
                 })
             })
         }
diff --git a/components/script/dom/nodeiterator.rs b/components/script/dom/nodeiterator.rs
index 27a99ec3b55..762d2233c6c 100644
--- a/components/script/dom/nodeiterator.rs
+++ b/components/script/dom/nodeiterator.rs
@@ -67,7 +67,7 @@ impl NodeIterator {
 impl NodeIteratorMethods for NodeIterator {
     // https://dom.spec.whatwg.org/#dom-nodeiterator-root
     fn Root(&self) -> Root<Node> {
-        self.root_node.root()
+        Root::from_ref(&*self.root_node)
     }
 
     // https://dom.spec.whatwg.org/#dom-nodeiterator-whattoshow
diff --git a/components/script/dom/nodelist.rs b/components/script/dom/nodelist.rs
index 490df73bd56..68e3b7ee424 100644
--- a/components/script/dom/nodelist.rs
+++ b/components/script/dom/nodelist.rs
@@ -66,7 +66,7 @@ impl NodeListMethods for NodeList {
     fn Item(&self, index: u32) -> Option<Root<Node>> {
         match self.list_type {
             NodeListType::Simple(ref elems) => {
-                elems.get(index as usize).map(|node| node.root())
+                elems.get(index as usize).map(|node| Root::from_ref(&**node))
             },
             NodeListType::Children(ref list) => list.item(index),
         }
diff --git a/components/script/dom/performance.rs b/components/script/dom/performance.rs
index b8b6c17ef09..591cb5472c4 100644
--- a/components/script/dom/performance.rs
+++ b/components/script/dom/performance.rs
@@ -46,7 +46,7 @@ impl Performance {
 impl PerformanceMethods for Performance {
     // https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/NavigationTiming/Overview.html#performance-timing-attribute
     fn Timing(&self) -> Root<PerformanceTiming> {
-        self.timing.root()
+        Root::from_ref(&*self.timing)
     }
 
     // https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/HighResolutionTime/Overview.html#dom-performance-now
diff --git a/components/script/dom/servohtmlparser.rs b/components/script/dom/servohtmlparser.rs
index 3a4a59ba3af..433c1085aef 100644
--- a/components/script/dom/servohtmlparser.rs
+++ b/components/script/dom/servohtmlparser.rs
@@ -45,7 +45,7 @@ impl Sink {
     #[allow(unrooted_must_root)] // method is only run at parse time
     pub fn get_or_create(&self, child: NodeOrText<JS<Node>>) -> Root<Node> {
         match child {
-            NodeOrText::AppendNode(n) => n.root(),
+            NodeOrText::AppendNode(n) => Root::from_ref(&*n),
             NodeOrText::AppendText(t) => {
                 let text = Text::new(t.into(), &self.document);
                 Root::upcast(text)
diff --git a/components/script/dom/touchlist.rs b/components/script/dom/touchlist.rs
index 5806f945008..f964a1ff250 100644
--- a/components/script/dom/touchlist.rs
+++ b/components/script/dom/touchlist.rs
@@ -38,7 +38,7 @@ impl TouchListMethods for TouchList {
 
     /// https://w3c.github.io/touch-events/#widl-TouchList-item-getter-Touch-unsigned-long-index
     fn Item(&self, index: u32) -> Option<Root<Touch>> {
-        self.touches.get(index as usize).map(JS::root)
+        self.touches.get(index as usize).map(|js| Root::from_ref(&**js))
     }
 
     /// https://w3c.github.io/touch-events/#widl-TouchList-item-getter-Touch-unsigned-long-index
diff --git a/components/script/dom/treewalker.rs b/components/script/dom/treewalker.rs
index f19e8383ddf..2bd5cc706e7 100644
--- a/components/script/dom/treewalker.rs
+++ b/components/script/dom/treewalker.rs
@@ -65,7 +65,7 @@ impl TreeWalker {
 impl TreeWalkerMethods for TreeWalker {
     // https://dom.spec.whatwg.org/#dom-treewalker-root
     fn Root(&self) -> Root<Node> {
-        self.root_node.root()
+        Root::from_ref(&*self.root_node)
     }
 
     // https://dom.spec.whatwg.org/#dom-treewalker-whattoshow
diff --git a/components/script/dom/webglrenderingcontext.rs b/components/script/dom/webglrenderingcontext.rs
index aa92967cb1e..07ac00000a2 100644
--- a/components/script/dom/webglrenderingcontext.rs
+++ b/components/script/dom/webglrenderingcontext.rs
@@ -153,7 +153,7 @@ impl WebGLRenderingContext {
     }
 
     fn mark_as_dirty(&self) {
-        self.canvas.root().upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
+        self.canvas.upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
     }
 }
 
@@ -166,7 +166,7 @@ impl Drop for WebGLRenderingContext {
 impl WebGLRenderingContextMethods for WebGLRenderingContext {
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.1
     fn Canvas(&self) -> Root<HTMLCanvasElement> {
-        self.canvas.root()
+        Root::from_ref(&*self.canvas)
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.1
@@ -848,8 +848,7 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
                     None => return,
                 };
 
-                let canvas = self.canvas.root();
-                let window = window_from_node(canvas.r());
+                let window = window_from_node(&*self.canvas);
 
                 let img = match canvas_utils::request_image_from_cache(window.r(), img_url) {
                     ImageResponse::Loaded(img) => img,
diff --git a/components/script/dom/xmlhttprequest.rs b/components/script/dom/xmlhttprequest.rs
index 39b86117b34..c5f8ef62556 100644
--- a/components/script/dom/xmlhttprequest.rs
+++ b/components/script/dom/xmlhttprequest.rs
@@ -465,7 +465,7 @@ impl XMLHttpRequestMethods for XMLHttpRequest {
 
     // https://xhr.spec.whatwg.org/#the-upload-attribute
     fn Upload(&self) -> Root<XMLHttpRequestUpload> {
-        self.upload.root()
+        Root::from_ref(&*self.upload)
     }
 
     // https://xhr.spec.whatwg.org/#the-send()-method
diff --git a/components/script/page.rs b/components/script/page.rs
index b6b35c6119a..67cb1ca46ed 100644
--- a/components/script/page.rs
+++ b/components/script/page.rs
@@ -68,11 +68,11 @@ impl Page {
     }
 
     pub fn window(&self) -> Root<Window> {
-        self.frame.borrow().as_ref().unwrap().window.root()
+        Root::from_ref(&*self.frame.borrow().as_ref().unwrap().window)
     }
 
     pub fn document(&self) -> Root<Document> {
-        self.frame.borrow().as_ref().unwrap().document.root()
+        Root::from_ref(&*self.frame.borrow().as_ref().unwrap().document)
     }
 
     // must handle root case separately
diff --git a/components/script/parse/html.rs b/components/script/parse/html.rs
index 4943fecdb5f..07c5d19b1f3 100644
--- a/components/script/parse/html.rs
+++ b/components/script/parse/html.rs
@@ -10,8 +10,7 @@ use dom::bindings::codegen::Bindings::HTMLTemplateElementBinding::HTMLTemplateEl
 use dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
 use dom::bindings::codegen::InheritTypes::{CharacterDataTypeId, NodeTypeId};
 use dom::bindings::conversions::Castable;
-use dom::bindings::js::{JS, Root};
-use dom::bindings::js::{RootedReference};
+use dom::bindings::js::{JS, RootedReference};
 use dom::characterdata::CharacterData;
 use dom::comment::Comment;
 use dom::document::Document;
@@ -45,11 +44,10 @@ impl<'a> TreeSink for servohtmlparser::Sink {
     type Handle = JS<Node>;
 
     fn get_document(&mut self) -> JS<Node> {
-        JS::from_ref(self.document.root().upcast())
+        JS::from_ref(self.document.upcast())
     }
 
     fn get_template_contents(&self, target: JS<Node>) -> JS<Node> {
-        let target = target.root();
         let template = target.downcast::<HTMLTemplateElement>()
             .expect("tried to get template contents of non-HTMLTemplateElement in HTML parsing");
         JS::from_ref(template.Content().upcast())
@@ -60,8 +58,7 @@ impl<'a> TreeSink for servohtmlparser::Sink {
     }
 
     fn elem_name(&self, target: JS<Node>) -> QualName {
-        let node: Root<Node> = target.root();
-        let elem = node.downcast::<Element>()
+        let elem = target.downcast::<Element>()
             .expect("tried to get name of non-Element in HTML parsing");
         QualName {
             ns: elem.namespace().clone(),
@@ -71,8 +68,7 @@ impl<'a> TreeSink for servohtmlparser::Sink {
 
     fn create_element(&mut self, name: QualName, attrs: Vec<Attribute>)
             -> JS<Node> {
-        let doc = self.document.root();
-        let elem = Element::create(name, None, doc.r(),
+        let elem = Element::create(name, None, &*self.document,
                                    ElementCreator::ParserCreated);
 
         for attr in attrs {
@@ -83,8 +79,7 @@ impl<'a> TreeSink for servohtmlparser::Sink {
     }
 
     fn create_comment(&mut self, text: StrTendril) -> JS<Node> {
-        let doc = self.document.root();
-        let comment = Comment::new(text.into(), doc.r());
+        let comment = Comment::new(text.into(), &*self.document);
         JS::from_ref(comment.upcast())
     }
 
@@ -92,14 +87,13 @@ impl<'a> TreeSink for servohtmlparser::Sink {
             sibling: JS<Node>,
             new_node: NodeOrText<JS<Node>>) -> Result<(), NodeOrText<JS<Node>>> {
         // If there is no parent, return the node to the parser.
-        let sibling: Root<Node> = sibling.root();
-        let parent = match sibling.r().GetParentNode() {
+        let parent = match sibling.GetParentNode() {
             Some(p) => p,
             None => return Err(new_node),
         };
 
         let child = self.get_or_create(new_node);
-        assert!(parent.r().InsertBefore(child.r(), Some(sibling.r())).is_ok());
+        assert!(parent.r().InsertBefore(child.r(), Some(&*sibling)).is_ok());
         Ok(())
     }
 
@@ -108,29 +102,26 @@ impl<'a> TreeSink for servohtmlparser::Sink {
     }
 
     fn set_quirks_mode(&mut self, mode: QuirksMode) {
-        let doc = self.document.root();
-        doc.r().set_quirks_mode(mode);
+        self.document.set_quirks_mode(mode);
     }
 
     fn append(&mut self, parent: JS<Node>, child: NodeOrText<JS<Node>>) {
-        let parent: Root<Node> = parent.root();
         let child = self.get_or_create(child);
 
         // FIXME(#3701): Use a simpler algorithm and merge adjacent text nodes
-        assert!(parent.r().AppendChild(child.r()).is_ok());
+        assert!(parent.AppendChild(child.r()).is_ok());
     }
 
     fn append_doctype_to_document(&mut self, name: StrTendril, public_id: StrTendril,
                                   system_id: StrTendril) {
-        let doc = self.document.root();
+        let doc = &*self.document;
         let doctype = DocumentType::new(
-            name.into(), Some(public_id.into()), Some(system_id.into()), doc.r());
+            name.into(), Some(public_id.into()), Some(system_id.into()), doc);
         doc.upcast::<Node>().AppendChild(doctype.upcast()).expect("Appending failed");
     }
 
     fn add_attrs_if_missing(&mut self, target: JS<Node>, attrs: Vec<Attribute>) {
-        let node: Root<Node> = target.root();
-        let elem = node.downcast::<Element>()
+        let elem = target.downcast::<Element>()
             .expect("tried to set attrs on non-Element in HTML parsing");
         for attr in attrs {
             elem.set_attribute_from_parser(attr.name, attr.value.into(), None);
@@ -138,20 +129,17 @@ impl<'a> TreeSink for servohtmlparser::Sink {
     }
 
     fn remove_from_parent(&mut self, target: JS<Node>) {
-        let node = target.root();
-        if let Some(ref parent) = node.r().GetParentNode() {
-            parent.r().RemoveChild(node.r()).unwrap();
+        if let Some(ref parent) = target.GetParentNode() {
+            parent.r().RemoveChild(&*target).unwrap();
         }
     }
 
     fn mark_script_already_started(&mut self, node: JS<Node>) {
-        let node: Root<Node> = node.root();
         let script = node.downcast::<HTMLScriptElement>();
         script.map(|script| script.mark_already_started());
     }
 
     fn complete_script(&mut self, node: JS<Node>) -> NextParserState {
-        let node: Root<Node> = node.root();
         let script = node.downcast::<HTMLScriptElement>();
         if let Some(script) = script {
             return script.prepare();
@@ -160,11 +148,7 @@ impl<'a> TreeSink for servohtmlparser::Sink {
     }
 
     fn reparent_children(&mut self, node: JS<Node>, new_parent: JS<Node>) {
-        let new_parent = new_parent.root();
-        let new_parent = new_parent.r();
-        let old_parent = node.root();
-        let old_parent = old_parent.r();
-        while let Some(ref child) = old_parent.GetFirstChild() {
+        while let Some(ref child) = node.GetFirstChild() {
             new_parent.AppendChild(child.r()).unwrap();
         }
 
@@ -181,11 +165,10 @@ impl<'a> Serializable for &'a Node {
                 let name = QualName::new(elem.namespace().clone(),
                                          elem.local_name().clone());
                 if traversal_scope == IncludeNode {
-                    let attrs = elem.attrs().iter().map(|at| {
-                        let attr = at.root();
-                        let qname = QualName::new(attr.r().namespace().clone(),
-                                                  attr.r().local_name().clone());
-                        let value = attr.r().value().clone();
+                    let attrs = elem.attrs().iter().map(|attr| {
+                        let qname = QualName::new(attr.namespace().clone(),
+                                                  attr.local_name().clone());
+                        let value = attr.value().clone();
                         (qname, value)
                     }).collect::<Vec<_>>();
                     let attr_refs = attrs.iter().map(|&(ref qname, ref value)| {
diff --git a/components/script/script_task.rs b/components/script/script_task.rs
index fa427db6ff1..4939a58e086 100644
--- a/components/script/script_task.rs
+++ b/components/script/script_task.rs
@@ -1747,9 +1747,8 @@ impl ScriptTask {
 
                 // Notify Constellation about the topmost anchor mouse over target.
                 for target in &*mouse_over_targets {
-                    let target = target.root();
                     if target.upcast::<Node>().is_anchor_element() {
-                        let status = target.r().get_attribute(&ns!(""), &atom!("href"))
+                        let status = target.get_attribute(&ns!(""), &atom!("href"))
                             .and_then(|href| {
                                 let value = href.value();
                                 let url = document.r().url();