Auto merge of #20447 - Brody-Eastwood:master, r=jdm

NCSU Canvas Rendering Project Initial Steps

<!-- Please describe your changes on the following line: -->
Implements the initial steps from:

https://github.com/servo/servo/wiki/Canvas-rendering-project

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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components/layout/display_list/builder.rs

@@ -1800,7 +1800,8 @@ impl FragmentDisplayListBuilding for Fragment {
                             let ipc_renderer = ipc_renderer.lock().unwrap();
                             let (sender, receiver) = ipc::channel().unwrap();
                             ipc_renderer
-                                .send(CanvasMsg::FromLayout(FromLayoutMsg::SendData(sender)))
+                                .send(CanvasMsg::FromLayout(FromLayoutMsg::SendData(sender),
+                                canvas_fragment_info.canvas_id.clone()))
                                 .unwrap();
                             (receiver.recv().unwrap().image_key, PixelFormat::BGRA8)
                         },

components/layout/fragment.rs

@@ -8,7 +8,7 @@
 
 use ServoArc;
 use app_units::Au;
-use canvas_traits::canvas::CanvasMsg;
+use canvas_traits::canvas::{CanvasMsg, CanvasId};
 use context::{LayoutContext, with_thread_local_font_context};
 use display_list::ToLayout;
 use euclid::{Point2D, Vector2D, Rect, Size2D};
@@ -345,6 +345,7 @@ pub struct CanvasFragmentInfo {
     pub source: CanvasFragmentSource,
     pub dom_width: Au,
     pub dom_height: Au,
+    pub canvas_id: CanvasId,
 }
 
 impl CanvasFragmentInfo {
@@ -362,6 +363,7 @@ impl CanvasFragmentInfo {
             source: source,
             dom_width: Au::from_px(data.width as i32),
             dom_height: Au::from_px(data.height as i32),
+            canvas_id: data.canvas_id,
         }
     }
 }