canvas: trace/instrument canvas messages processing (#38600)

Add some tracing/instrumenting for canvas messages processing.

Testing: We have not tests for tracing code.

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

components/canvas/Cargo.toml

@@ -15,6 +15,7 @@ path = "lib.rs"
 vello = ["dep:vello", "dep:pollster", "dep:futures-intrusive", "dep:peniko"]
 vello_cpu = ["dep:vello_cpu", "dep:peniko"]
 raqote = ["dep:raqote", "dep:font-kit"]
+tracing = ["dep:tracing"]
 
 [dependencies]
 app_units = { workspace = true }
@@ -43,3 +44,6 @@ vello = { workspace = true, optional = true }
 vello_cpu = { workspace = true, optional = true }
 pollster = { version = "0.4", optional = true }
 futures-intrusive = { version = "0.5", optional = true }
+
+tracing = { workspace = true, optional = true }
+servo-tracing = { workspace = true }

components/canvas/canvas_data.rs

@@ -641,7 +641,15 @@ impl<DrawTarget: GenericDrawTarget> CanvasData<DrawTarget> {
 
     /// Update image in WebRender
     pub(crate) fn update_image_rendering(&mut self) {
-        let (descriptor, data) = self.drawtarget.image_descriptor_and_serializable_data();
+        let (descriptor, data) = {
+            #[cfg(feature = "tracing")]
+            let _span = tracing::trace_span!(
+                "image_descriptor_and_serializable_data",
+                servo_profiling = true,
+            )
+            .entered();
+            self.drawtarget.image_descriptor_and_serializable_data()
+        };
 
         self.compositor_api
             .update_image(self.image_key, descriptor, data);
@@ -732,7 +740,7 @@ impl<DrawTarget: GenericDrawTarget> CanvasData<DrawTarget> {
     /// It reads image data from the canvas
     /// canvas_size: The size of the canvas we're reading from
     /// read_rect: The area of the canvas we want to read from
-    #[allow(unsafe_code)]
+    #[servo_tracing::instrument(skip_all)]
     pub(crate) fn read_pixels(&mut self, read_rect: Option<Rect<u32>>) -> Snapshot {
         let canvas_size = self.drawtarget.get_size().cast();
 

components/canvas/canvas_paint_thread.rs

@@ -106,6 +106,7 @@ impl CanvasPaintThread {
         (create_sender, ipc_sender)
     }
 
+    #[servo_tracing::instrument(skip_all)]
     pub fn create_canvas(&mut self, size: Size2D<u64>) -> Option<(CanvasId, ImageKey)> {
         let canvas_id = self.next_canvas_id;
         self.next_canvas_id.0 += 1;
@@ -117,6 +118,10 @@ impl CanvasPaintThread {
         Some((canvas_id, image_key))
     }
 
+    #[servo_tracing::instrument(
+        skip_all,
+        fields(message = message.to_string())
+    )]
     fn process_canvas_2d_message(&mut self, message: Canvas2dMsg, canvas_id: CanvasId) {
         match message {
             Canvas2dMsg::FillText(