Make DOM own the style and layout data, in an UnsafeCell

The previous Cell was a lie.

components/layout/query.rs

@@ -1036,7 +1036,7 @@ fn inner_text_collection_steps<'dom>(
             _ => child,
         };
 
-        let element_data = unsafe {
+        let element_data = {
             &node.get_style_and_layout_data().as_ref().map(|opaque| {
                 &opaque
                     .downcast_ref::<StyleAndLayoutData>()

components/layout/traversal.rs

@@ -73,7 +73,7 @@ where
         // flow construction:
         // (1) They child doesn't yet have layout data (preorder traversal initializes it).
         // (2) The parent element has restyle damage (so the text flow also needs fixup).
-        (unsafe { node.get_raw_data().is_none() }) || !parent_data.damage.is_empty()
+        node.get_raw_data().is_none() || !parent_data.damage.is_empty()
     }
 
     fn shared_context(&self) -> &SharedStyleContext {

components/layout/wrapper.rs

@@ -39,24 +39,22 @@ use style::selector_parser::RestyleDamage;
 use style::values::computed::counters::ContentItem;
 use style::values::generics::counters::Content;
 
-pub trait LayoutNodeLayoutData {
-    /// Similar to borrow_data*, but returns the full PersistentLayoutData rather
-    /// than only the style::data::ElementData.
-    fn borrow_layout_data(&self) -> Option<AtomicRef<LayoutData>>;
-    fn mutate_layout_data(&self) -> Option<AtomicRefMut<LayoutData>>;
+pub trait LayoutNodeLayoutData<'dom> {
+    fn borrow_layout_data(self) -> Option<AtomicRef<'dom, LayoutData>>;
+    fn mutate_layout_data(self) -> Option<AtomicRefMut<'dom, LayoutData>>;
     fn flow_debug_id(self) -> usize;
 }
 
-impl<'dom, T> LayoutNodeLayoutData for T
+impl<'dom, T> LayoutNodeLayoutData<'dom> for T
 where
     T: GetLayoutData<'dom>,
 {
-    fn borrow_layout_data(&self) -> Option<AtomicRef<LayoutData>> {
-        unsafe { self.get_raw_data().map(|d| d.layout_data.borrow()) }
+    fn borrow_layout_data(self) -> Option<AtomicRef<'dom, LayoutData>> {
+        self.get_raw_data().map(|d| d.layout_data.borrow())
     }
 
-    fn mutate_layout_data(&self) -> Option<AtomicRefMut<LayoutData>> {
-        unsafe { self.get_raw_data().map(|d| d.layout_data.borrow_mut()) }
+    fn mutate_layout_data(self) -> Option<AtomicRefMut<'dom, LayoutData>> {
+        self.get_raw_data().map(|d| d.layout_data.borrow_mut())
     }
 
     fn flow_debug_id(self) -> usize {
@@ -65,15 +63,15 @@ where
     }
 }
 
-pub trait GetRawData {
-    unsafe fn get_raw_data(&self) -> Option<&StyleAndLayoutData>;
+pub trait GetRawData<'dom> {
+    fn get_raw_data(self) -> Option<&'dom StyleAndLayoutData>;
 }
 
-impl<'dom, T> GetRawData for T
+impl<'dom, T> GetRawData<'dom> for T
 where
     T: GetLayoutData<'dom>,
 {
-    unsafe fn get_raw_data(&self) -> Option<&StyleAndLayoutData> {
+    fn get_raw_data(self) -> Option<&'dom StyleAndLayoutData> {
         self.get_style_and_layout_data()
             .map(|opaque| opaque.downcast_ref().unwrap())
     }
@@ -144,7 +142,7 @@ where
             debug_assert!(node.is_element());
         }
 
-        let damage = unsafe {
+        let damage = {
             let data = node.get_raw_data().unwrap();
 
             if !data

components/layout_2020/dom_traversal.rs

@@ -369,7 +369,7 @@ pub(crate) trait NodeExt<'dom>: 'dom + Copy + LayoutNode<'dom> + Send + Sync {
     fn style(self, context: &LayoutContext) -> ServoArc<ComputedValues>;
 
     fn as_opaque(self) -> OpaqueNode;
-    fn layout_data_mut(&self) -> AtomicRefMut<LayoutDataForElement>;
+    fn layout_data_mut(self) -> AtomicRefMut<'dom, LayoutDataForElement>;
     fn element_box_slot(&self) -> BoxSlot<'dom>;
     fn pseudo_element_box_slot(&self, which: WhichPseudoElement) -> BoxSlot<'dom>;
     fn unset_pseudo_element_box(self, which: WhichPseudoElement);
@@ -447,12 +447,10 @@ where
     }
 
     #[allow(unsafe_code)]
-    fn layout_data_mut(&self) -> AtomicRefMut<LayoutDataForElement> {
-        unsafe {
-            self.get_raw_data()
-                .map(|d| d.layout_data.borrow_mut())
-                .unwrap()
-        }
+    fn layout_data_mut(self) -> AtomicRefMut<'dom, LayoutDataForElement> {
+        self.get_raw_data()
+            .map(|d| d.layout_data.borrow_mut())
+            .unwrap()
     }
 
     fn element_box_slot(&self) -> BoxSlot<'dom> {

components/layout_2020/traversal.rs

@@ -63,7 +63,7 @@ where
     }
 
     fn text_node_needs_traversal(node: E::ConcreteNode, parent_data: &ElementData) -> bool {
-        (unsafe { node.get_raw_data().is_none() }) || !parent_data.damage.is_empty()
+        node.get_raw_data().is_none() || !parent_data.damage.is_empty()
     }
 
     fn shared_context(&self) -> &SharedStyleContext {

components/layout_2020/wrapper.rs

@@ -7,15 +7,15 @@
 use crate::data::StyleAndLayoutData;
 use script_layout_interface::wrapper_traits::GetLayoutData;
 
-pub trait GetRawData {
-    unsafe fn get_raw_data(&self) -> Option<&StyleAndLayoutData>;
+pub trait GetRawData<'dom> {
+    fn get_raw_data(self) -> Option<&'dom StyleAndLayoutData>;
 }
 
-impl<'dom, T> GetRawData for T
+impl<'dom, T> GetRawData<'dom> for T
 where
     T: GetLayoutData<'dom>,
 {
-    unsafe fn get_raw_data(&self) -> Option<&StyleAndLayoutData> {
+    fn get_raw_data(self) -> Option<&'dom StyleAndLayoutData> {
         self.get_style_and_layout_data()
             .map(|opaque| opaque.downcast_ref().unwrap())
     }

components/layout_thread/dom_wrapper.rs

@@ -91,10 +91,6 @@ use style::str::is_whitespace;
 use style::stylist::CascadeData;
 use style::CaseSensitivityExt;
 
-pub unsafe fn drop_style_and_layout_data(data: OpaqueStyleAndLayoutData) {
-    drop(Box::from_raw(data.as_ptr()));
-}
-
 #[derive(Clone, Copy)]
 pub struct ServoLayoutNode<'dom> {
     /// The wrapped node.
@@ -234,7 +230,7 @@ impl<'ln> TNode for ServoLayoutNode<'ln> {
     }
 
     fn opaque(&self) -> OpaqueNode {
-        unsafe { self.get_jsmanaged().opaque() }
+        self.get_jsmanaged().opaque()
     }
 
     fn debug_id(self) -> usize {
@@ -291,34 +287,33 @@ impl<'ln> LayoutNode<'ln> for ServoLayoutNode<'ln> {
     }
 }
 
-impl<'ln> GetLayoutData<'ln> for ServoLayoutNode<'ln> {
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
-        unsafe { self.get_jsmanaged().get_style_and_layout_data() }
+impl<'dom> GetLayoutData<'dom> for ServoLayoutNode<'dom> {
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData> {
+        self.get_jsmanaged().get_style_and_layout_data()
     }
 }
 
-impl<'le> GetLayoutData<'le> for ServoLayoutElement<'le> {
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
+impl<'dom> GetLayoutData<'dom> for ServoLayoutElement<'dom> {
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData> {
         self.as_node().get_style_and_layout_data()
     }
 }
 
-impl<'ln> GetLayoutData<'ln> for ServoThreadSafeLayoutNode<'ln> {
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
+impl<'dom> GetLayoutData<'dom> for ServoThreadSafeLayoutNode<'dom> {
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData> {
         self.node.get_style_and_layout_data()
     }
 }
 
-impl<'le> GetLayoutData<'le> for ServoThreadSafeLayoutElement<'le> {
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
+impl<'dom> GetLayoutData<'dom> for ServoThreadSafeLayoutElement<'dom> {
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData> {
         self.element.as_node().get_style_and_layout_data()
     }
 }
 
-impl<'ln> ServoLayoutNode<'ln> {
-    /// Returns the interior of this node as a `LayoutDom`. This is highly unsafe for layout to
-    /// call and as such is marked `unsafe`.
-    pub unsafe fn get_jsmanaged(&self) -> LayoutDom<'ln, Node> {
+impl<'dom> ServoLayoutNode<'dom> {
+    /// Returns the interior of this node as a `LayoutDom`.
+    pub fn get_jsmanaged(self) -> LayoutDom<'dom, Node> {
         self.node
     }
 }
@@ -542,7 +537,7 @@ impl<'le> TElement for ServoLayoutElement<'le> {
 
     unsafe fn clear_data(&self) {
         if self.get_raw_data().is_some() {
-            drop_style_and_layout_data(self.as_node().take_style_and_layout_data());
+            drop(self.as_node().take_style_and_layout_data());
         }
     }
 
@@ -700,7 +695,7 @@ impl<'le> ServoLayoutElement<'le> {
     }
 
     fn get_style_data(&self) -> Option<&StyleData> {
-        self.get_style_and_layout_data().map(|opaque| unsafe {
+        self.get_style_and_layout_data().map(|opaque| {
             &opaque
                 .downcast_ref::<StyleAndLayoutData>()
                 .unwrap()
@@ -1065,7 +1060,7 @@ impl<'ln> ThreadSafeLayoutNode<'ln> for ServoThreadSafeLayoutNode<'ln> {
             })
     }
 
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
+    fn get_style_and_layout_data(self) -> Option<&'ln OpaqueStyleAndLayoutData> {
         self.node.get_style_and_layout_data()
     }
 

components/layout_thread/lib.rs

@@ -23,7 +23,6 @@ extern crate profile_traits;
 
 mod dom_wrapper;
 
-use crate::dom_wrapper::drop_style_and_layout_data;
 use crate::dom_wrapper::{ServoLayoutDocument, ServoLayoutElement, ServoLayoutNode};
 use app_units::Au;
 use crossbeam_channel::{unbounded, Receiver, Sender};
@@ -692,7 +691,6 @@ impl LayoutThread {
             Msg::GetRPC(..) => LayoutHangAnnotation::GetRPC,
             Msg::TickAnimations(..) => LayoutHangAnnotation::TickAnimations,
             Msg::AdvanceClockMs(..) => LayoutHangAnnotation::AdvanceClockMs,
-            Msg::ReapStyleAndLayoutData(..) => LayoutHangAnnotation::ReapStyleAndLayoutData,
             Msg::CollectReports(..) => LayoutHangAnnotation::CollectReports,
             Msg::PrepareToExit(..) => LayoutHangAnnotation::PrepareToExit,
             Msg::ExitNow => LayoutHangAnnotation::ExitNow,
@@ -833,9 +831,6 @@ impl LayoutThread {
                     webrender_api::ScrollClamping::ToContentBounds,
                 );
             },
-            Msg::ReapStyleAndLayoutData(dead_data) => unsafe {
-                drop_style_and_layout_data(dead_data)
-            },
             Msg::CollectReports(reports_chan) => {
                 self.collect_reports(reports_chan, possibly_locked_rw_data);
             },
@@ -967,9 +962,6 @@ impl LayoutThread {
         response_chan.send(()).unwrap();
         loop {
             match self.port.recv().unwrap() {
-                Msg::ReapStyleAndLayoutData(dead_data) => unsafe {
-                    drop_style_and_layout_data(dead_data)
-                },
                 Msg::ExitNow => {
                     debug!("layout thread is exiting...");
                     self.exit_now();

components/layout_thread_2020/dom_wrapper.rs

@@ -91,10 +91,6 @@ use style::str::is_whitespace;
 use style::stylist::CascadeData;
 use style::CaseSensitivityExt;
 
-pub unsafe fn drop_style_and_layout_data(data: OpaqueStyleAndLayoutData) {
-    drop(Box::from_raw(data.as_ptr()));
-}
-
 #[derive(Clone, Copy)]
 pub struct ServoLayoutNode<'dom> {
     /// The wrapped node.
@@ -298,26 +294,26 @@ impl<'ln> LayoutNode<'ln> for ServoLayoutNode<'ln> {
     }
 }
 
-impl<'ln> GetLayoutData<'ln> for ServoLayoutNode<'ln> {
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
+impl<'dom> GetLayoutData<'dom> for ServoLayoutNode<'dom> {
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData> {
         unsafe { self.get_jsmanaged().get_style_and_layout_data() }
     }
 }
 
-impl<'le> GetLayoutData<'le> for ServoLayoutElement<'le> {
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
+impl<'dom> GetLayoutData<'dom> for ServoLayoutElement<'dom> {
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData> {
         self.as_node().get_style_and_layout_data()
     }
 }
 
-impl<'ln> GetLayoutData<'ln> for ServoThreadSafeLayoutNode<'ln> {
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
+impl<'dom> GetLayoutData<'dom> for ServoThreadSafeLayoutNode<'dom> {
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData> {
         self.node.get_style_and_layout_data()
     }
 }
 
-impl<'le> GetLayoutData<'le> for ServoThreadSafeLayoutElement<'le> {
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
+impl<'dom> GetLayoutData<'dom> for ServoThreadSafeLayoutElement<'dom> {
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData> {
         self.element.as_node().get_style_and_layout_data()
     }
 }
@@ -549,7 +545,7 @@ impl<'le> TElement for ServoLayoutElement<'le> {
 
     unsafe fn clear_data(&self) {
         if self.get_raw_data().is_some() {
-            drop_style_and_layout_data(self.as_node().take_style_and_layout_data());
+            drop(self.as_node().take_style_and_layout_data());
         }
     }
 
@@ -707,7 +703,7 @@ impl<'le> ServoLayoutElement<'le> {
     }
 
     fn get_style_data(&self) -> Option<&StyleData> {
-        self.get_style_and_layout_data().map(|opaque| unsafe {
+        self.get_style_and_layout_data().map(|opaque| {
             &opaque
                 .downcast_ref::<StyleAndLayoutData>()
                 .unwrap()
@@ -1072,7 +1068,7 @@ impl<'ln> ThreadSafeLayoutNode<'ln> for ServoThreadSafeLayoutNode<'ln> {
             })
     }
 
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData> {
+    fn get_style_and_layout_data(self) -> Option<&'ln OpaqueStyleAndLayoutData> {
         self.node.get_style_and_layout_data()
     }
 

components/layout_thread_2020/lib.rs

@@ -21,7 +21,6 @@ extern crate profile_traits;
 
 mod dom_wrapper;
 
-use crate::dom_wrapper::drop_style_and_layout_data;
 use crate::dom_wrapper::{ServoLayoutDocument, ServoLayoutElement, ServoLayoutNode};
 use app_units::Au;
 use crossbeam_channel::{unbounded, Receiver, Sender};
@@ -640,7 +639,6 @@ impl LayoutThread {
             Msg::GetRPC(..) => LayoutHangAnnotation::GetRPC,
             Msg::TickAnimations(..) => LayoutHangAnnotation::TickAnimations,
             Msg::AdvanceClockMs(..) => LayoutHangAnnotation::AdvanceClockMs,
-            Msg::ReapStyleAndLayoutData(..) => LayoutHangAnnotation::ReapStyleAndLayoutData,
             Msg::CollectReports(..) => LayoutHangAnnotation::CollectReports,
             Msg::PrepareToExit(..) => LayoutHangAnnotation::PrepareToExit,
             Msg::ExitNow => LayoutHangAnnotation::ExitNow,
@@ -779,9 +777,6 @@ impl LayoutThread {
                     webrender_api::ScrollClamping::ToContentBounds,
                 );
             },
-            Msg::ReapStyleAndLayoutData(dead_data) => unsafe {
-                drop_style_and_layout_data(dead_data)
-            },
             Msg::CollectReports(reports_chan) => {
                 self.collect_reports(reports_chan, possibly_locked_rw_data);
             },
@@ -890,9 +885,6 @@ impl LayoutThread {
         response_chan.send(()).unwrap();
         loop {
             match self.port.recv().unwrap() {
-                Msg::ReapStyleAndLayoutData(dead_data) => unsafe {
-                    drop_style_and_layout_data(dead_data)
-                },
                 Msg::ExitNow => {
                     debug!("layout thread is exiting...");
                     self.exit_now();

components/msg/constellation_msg.rs

@@ -532,7 +532,6 @@ pub enum LayoutHangAnnotation {
     GetRPC,
     TickAnimations,
     AdvanceClockMs,
-    ReapStyleAndLayoutData,
     CollectReports,
     PrepareToExit,
     ExitNow,

components/script/dom/node.rs

@@ -65,7 +65,6 @@ use crate::dom::virtualmethods::{vtable_for, VirtualMethods};
 use crate::dom::window::Window;
 use crate::script_thread::ScriptThread;
 use app_units::Au;
-use crossbeam_channel::Sender;
 use devtools_traits::NodeInfo;
 use dom_struct::dom_struct;
 use euclid::default::{Point2D, Rect, Size2D, Vector2D};
@@ -76,7 +75,6 @@ use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
 use msg::constellation_msg::{BrowsingContextId, PipelineId};
 use net_traits::image::base::{Image, ImageMetadata};
 use ref_slice::ref_slice;
-use script_layout_interface::message::Msg;
 use script_layout_interface::{HTMLCanvasData, HTMLMediaData, LayoutElementType, LayoutNodeType};
 use script_layout_interface::{OpaqueStyleAndLayoutData, SVGSVGData, TrustedNodeAddress};
 use script_traits::DocumentActivity;
@@ -99,7 +97,6 @@ use style::context::QuirksMode;
 use style::dom::OpaqueNode;
 use style::selector_parser::{SelectorImpl, SelectorParser};
 use style::stylesheets::Stylesheet;
-use style::thread_state;
 use uuid::Uuid;
 
 //
@@ -155,7 +152,8 @@ pub struct Node {
     ///
     /// Must be sent back to the layout thread to be destroyed when this
     /// node is finalized.
-    style_and_layout_data: Cell<Option<OpaqueStyleAndLayoutData>>,
+    #[ignore_malloc_size_of = "shrug"]
+    style_and_layout_data: UnsafeCell<Option<OpaqueStyleAndLayoutData>>,
 }
 
 bitflags! {
@@ -205,15 +203,6 @@ impl NodeFlags {
     }
 }
 
-impl Drop for Node {
-    #[allow(unsafe_code)]
-    fn drop(&mut self) {
-        if let Some(data) = self.style_and_layout_data.get() {
-            self.dispose(data, ScriptThread::get_any_layout_chan().as_ref());
-        }
-    }
-}
-
 /// suppress observers flag
 /// <https://dom.spec.whatwg.org/#concept-node-insert>
 /// <https://dom.spec.whatwg.org/#concept-node-remove>
@@ -224,21 +213,6 @@ enum SuppressObserver {
 }
 
 impl Node {
-    /// Sends the style and layout data, if any, back to the layout thread to be destroyed.
-    pub(crate) fn dispose(
-        &self,
-        data: OpaqueStyleAndLayoutData,
-        layout_chan: Option<&Sender<Msg>>,
-    ) {
-        debug_assert!(thread_state::get().is_script());
-        self.style_and_layout_data.set(None);
-        if layout_chan.map_or(false, |chan| {
-            chan.send(Msg::ReapStyleAndLayoutData(data)).is_err()
-        }) {
-            warn!("layout thread unreachable - leaking layout data");
-        }
-    }
-
     /// Adds a new child to the end of this node's list of children.
     ///
     /// Fails unless `new_child` is disconnected from the tree.
@@ -317,16 +291,11 @@ impl Node {
                 false,
             );
         }
-        let window = window_from_node(root);
-        let layout_chan = window.layout_chan();
         for node in root.traverse_preorder(ShadowIncluding::Yes) {
             // This needs to be in its own loop, because unbind_from_tree may
             // rely on the state of IS_IN_DOC of the context node's descendants,
             // e.g. when removing a <form>.
             vtable_for(&&*node).unbind_from_tree(&context);
-            if let Some(data) = node.style_and_layout_data.get() {
-                node.dispose(data, Some(layout_chan));
-            }
             // https://dom.spec.whatwg.org/#concept-node-remove step 14
             if let Some(element) = node.as_custom_element() {
                 ScriptThread::enqueue_callback_reaction(
@@ -507,15 +476,6 @@ impl<'a> Iterator for QuerySelectorIterator {
 impl Node {
     impl_rare_data!(NodeRareData);
 
-    pub(crate) fn teardown(&self, layout_chan: &Sender<Msg>) {
-        if let Some(data) = self.style_and_layout_data.get() {
-            self.dispose(data, Some(layout_chan));
-        }
-        for kid in self.children() {
-            kid.teardown(layout_chan);
-        }
-    }
-
     /// Returns true if this node is before `other` in the same connected DOM
     /// tree.
     pub fn is_before(&self, other: &Node) -> bool {
@@ -1322,8 +1282,8 @@ pub trait LayoutNodeHelpers<'dom> {
 
     fn children_count(self) -> u32;
 
-    unsafe fn get_style_and_layout_data(self) -> Option<OpaqueStyleAndLayoutData>;
-    unsafe fn init_style_and_layout_data(self, _: OpaqueStyleAndLayoutData);
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData>;
+    unsafe fn init_style_and_layout_data(self, data: OpaqueStyleAndLayoutData);
     unsafe fn take_style_and_layout_data(self) -> OpaqueStyleAndLayoutData;
 
     fn text_content(self) -> Cow<'dom, str>;
@@ -1450,23 +1410,24 @@ impl<'dom> LayoutNodeHelpers<'dom> for LayoutDom<'dom, Node> {
 
     #[inline]
     #[allow(unsafe_code)]
-    unsafe fn get_style_and_layout_data(self) -> Option<OpaqueStyleAndLayoutData> {
-        (*self.unsafe_get()).style_and_layout_data.get()
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData> {
+        unsafe { (*self.unsafe_get().style_and_layout_data.get()).as_ref() }
     }
 
     #[inline]
     #[allow(unsafe_code)]
     unsafe fn init_style_and_layout_data(self, val: OpaqueStyleAndLayoutData) {
-        debug_assert!((*self.unsafe_get()).style_and_layout_data.get().is_none());
-        (*self.unsafe_get()).style_and_layout_data.set(Some(val));
+        let data = &mut *self.unsafe_get().style_and_layout_data.get();
+        debug_assert!(data.is_none());
+        *data = Some(val);
     }
 
     #[inline]
     #[allow(unsafe_code)]
     unsafe fn take_style_and_layout_data(self) -> OpaqueStyleAndLayoutData {
-        let val = (*self.unsafe_get()).style_and_layout_data.get().unwrap();
-        (*self.unsafe_get()).style_and_layout_data.set(None);
-        val
+        (*self.unsafe_get().style_and_layout_data.get())
+            .take()
+            .unwrap()
     }
 
     fn text_content(self) -> Cow<'dom, str> {
@@ -1781,7 +1742,7 @@ impl Node {
             inclusive_descendants_version: Cell::new(0),
             ranges: WeakRangeVec::new(),
 
-            style_and_layout_data: Cell::new(None),
+            style_and_layout_data: UnsafeCell::new(None),
         }
     }
 

components/script/dom/window.rs

@@ -1399,13 +1399,6 @@ impl Window {
     }
 
     pub fn clear_js_runtime(&self) {
-        // We tear down the active document, which causes all the attached
-        // nodes to dispose of their layout data. This messages the layout
-        // thread, informing it that it can safely free the memory.
-        self.Document()
-            .upcast::<Node>()
-            .teardown(self.layout_chan());
-
         // Remove the infra for managing messageports and broadcast channels.
         self.upcast::<GlobalScope>().remove_web_messaging_infra();
 

components/script/script_thread.rs

@@ -822,23 +822,6 @@ impl ScriptThreadFactory for ScriptThread {
 }
 
 impl ScriptThread {
-    pub(crate) fn get_any_layout_chan() -> Option<Sender<Msg>> {
-        SCRIPT_THREAD_ROOT.with(|root| {
-            let script_thread = match root.get() {
-                Some(s) => unsafe { &*s },
-                None => return None,
-            };
-            script_thread
-                .documents
-                .borrow()
-                .map
-                .values()
-                .next()
-                .map(|d| d.window().layout_chan())
-                .cloned()
-        })
-    }
-
     pub fn runtime_handle() -> ParentRuntime {
         SCRIPT_THREAD_ROOT.with(|root| {
             let script_thread = unsafe { &*root.get().unwrap() };

components/script_layout_interface/lib.rs

@@ -26,7 +26,6 @@ use net_traits::image_cache::PendingImageId;
 use script_traits::UntrustedNodeAddress;
 use servo_url::{ImmutableOrigin, ServoUrl};
 use std::any::Any;
-use std::ptr::NonNull;
 use std::sync::atomic::AtomicIsize;
 use style::data::ElementData;
 
@@ -51,12 +50,11 @@ impl StyleData {
     }
 }
 
-#[derive(Clone, Copy, MallocSizeOf)]
+#[derive(MallocSizeOf)]
 pub struct OpaqueStyleAndLayoutData {
     // NB: We really store a `StyleAndLayoutData` here, so be careful!
-    #[ignore_malloc_size_of = "TODO(#6910) Box value that should be counted but \
-                               the type lives in layout"]
-    ptr: NonNull<dyn Any + Send + Sync>,
+    #[ignore_malloc_size_of = "Trait objects are hard"]
+    ptr: Box<dyn Any + Send + Sync>,
 }
 
 impl OpaqueStyleAndLayoutData {
@@ -66,23 +64,17 @@ impl OpaqueStyleAndLayoutData {
         T: Any + Send + Sync,
     {
         Self {
-            ptr: Box::into_raw_non_null(Box::new(value) as Box<dyn Any + Send + Sync>),
+            ptr: Box::new(value) as Box<dyn Any + Send + Sync>,
         }
     }
 
-    #[inline]
-    pub fn as_ptr(&self) -> *mut (dyn Any + Send + Sync) {
-        self.ptr.as_ptr()
-    }
-
     /// Extremely cursed.
-    #[allow(unsafe_code)]
     #[inline]
-    pub unsafe fn downcast_ref<'extended, T>(&self) -> Option<&'extended T>
+    pub fn downcast_ref<T>(&self) -> Option<&T>
     where
         T: Any + Send + Sync,
     {
-        (*self.ptr.as_ptr()).downcast_ref()
+        self.ptr.downcast_ref()
     }
 }
 

components/script_layout_interface/message.rs

@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::rpc::LayoutRPC;
-use crate::{OpaqueStyleAndLayoutData, PendingImage, TrustedNodeAddress};
+use crate::{PendingImage, TrustedNodeAddress};
 use app_units::Au;
 use crossbeam_channel::{Receiver, Sender};
 use euclid::default::{Point2D, Rect};
@@ -56,11 +56,6 @@ pub enum Msg {
     /// field is whether animations should be force-ticked.
     AdvanceClockMs(i32, bool, ImmutableOrigin),
 
-    /// Destroys layout data associated with a DOM node.
-    ///
-    /// TODO(pcwalton): Maybe think about batching to avoid message traffic.
-    ReapStyleAndLayoutData(OpaqueStyleAndLayoutData),
-
     /// Requests that the layout thread measure its memory usage. The resulting reports are sent back
     /// via the supplied channel.
     CollectReports(ReportsChan),

components/script_layout_interface/wrapper_traits.rs

@@ -80,7 +80,7 @@ impl PseudoElementType {
 
 /// Trait to abstract access to layout data across various data structures.
 pub trait GetLayoutData<'dom> {
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData>;
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData>;
 }
 
 /// A wrapper so that layout can access only the methods that it should have access to. Layout must
@@ -224,7 +224,7 @@ pub trait ThreadSafeLayoutNode<'dom>:
             .map_or(PseudoElementType::Normal, |el| el.get_pseudo_element_type())
     }
 
-    fn get_style_and_layout_data(&self) -> Option<OpaqueStyleAndLayoutData>;
+    fn get_style_and_layout_data(self) -> Option<&'dom OpaqueStyleAndLayoutData>;
 
     fn style(&self, context: &SharedStyleContext) -> Arc<ComputedValues> {
         if let Some(el) = self.as_element() {