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

The previous Cell was a lie.

2 files changed, 11 insertions, 23 deletions

diff --git a/components/layout_thread_2020/dom_wrapper.rs b/components/layout_thread_2020/dom_wrapper.rs
index bbca53acc62..b396eeee5cc 100644
--- a/components/layout_thread_2020/dom_wrapper.rs
+++ b/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()
     }
 
diff --git a/components/layout_thread_2020/lib.rs b/components/layout_thread_2020/lib.rs
index 3e2b73875fe..812a8823f38 100644
--- a/components/layout_thread_2020/lib.rs
+++ b/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();