canvas: Send CanvasClose to canvas thread from canvas state (#38315)

Currently we only closed `CanvasRenderingContext2D` (and
`OffscreenCanvasRenderingContext2D` because it wraps
`CanvasRenderingContext2D`), but we didn't close last consumer of
`CanvasState` which is `PaintRenderingContext`. To prevent any future
leaks, let's just send `CanvasClose` in `CanvasState` drop.

Testing: Existing WPT tests

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/script/canvas_state.rs

@@ -259,10 +259,6 @@ impl CanvasState {
         })
     }
 
-    pub(crate) fn get_ipc_renderer(&self) -> &IpcSender<CanvasMsg> {
-        &self.ipc_renderer
-    }
-
     pub(crate) fn image_key(&self) -> ImageKey {
         self.image_key
     }
@@ -2197,6 +2193,14 @@ impl CanvasState {
     }
 }
 
+impl Drop for CanvasState {
+    fn drop(&mut self) {
+        if let Err(err) = self.ipc_renderer.send(CanvasMsg::Close(self.canvas_id)) {
+            warn!("Could not close canvas: {}", err)
+        }
+    }
+}
+
 pub(crate) fn parse_color(
     canvas: Option<&HTMLCanvasElement>,
     string: &str,

components/script/dom/canvasrenderingcontext2d.rs

@@ -2,10 +2,10 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use canvas_traits::canvas::{Canvas2dMsg, CanvasId, CanvasMsg};
+use canvas_traits::canvas::{Canvas2dMsg, CanvasId};
 use dom_struct::dom_struct;
 use euclid::default::Size2D;
-use ipc_channel::ipc::{self, IpcSender};
+use ipc_channel::ipc;
 use pixels::Snapshot;
 use script_bindings::inheritance::Castable;
 use servo_url::ServoUrl;
@@ -37,29 +37,12 @@ use crate::dom::path2d::Path2D;
 use crate::dom::textmetrics::TextMetrics;
 use crate::script_runtime::CanGc;
 
-#[derive(JSTraceable, MallocSizeOf)]
-struct DroppableCanvasRenderingContext2D {
-    #[no_trace]
-    ipc_sender: IpcSender<CanvasMsg>,
-    #[no_trace]
-    canvas_id: CanvasId,
-}
-
-impl Drop for DroppableCanvasRenderingContext2D {
-    fn drop(&mut self) {
-        if let Err(err) = self.ipc_sender.send(CanvasMsg::Close(self.canvas_id)) {
-            warn!("Could not close canvas: {}", err)
-        }
-    }
-}
-
 // https://html.spec.whatwg.org/multipage/#canvasrenderingcontext2d
 #[dom_struct]
 pub(crate) struct CanvasRenderingContext2D {
     reflector_: Reflector,
     canvas: HTMLCanvasElementOrOffscreenCanvas,
     canvas_state: CanvasState,
-    droppable: DroppableCanvasRenderingContext2D,
 }
 
 impl CanvasRenderingContext2D {
@@ -71,16 +54,10 @@ impl CanvasRenderingContext2D {
     ) -> Option<CanvasRenderingContext2D> {
         let canvas_state =
             CanvasState::new(global, Size2D::new(size.width as u64, size.height as u64))?;
-        let ipc_sender = canvas_state.get_ipc_renderer().clone();
-        let canvas_id = canvas_state.get_canvas_id();
         Some(CanvasRenderingContext2D {
             reflector_: Reflector::new(),
             canvas,
             canvas_state,
-            droppable: DroppableCanvasRenderingContext2D {
-                ipc_sender,
-                canvas_id,
-            },
         })
     }