WIP: move OffscreenCanvas into new display compositor

cc/ipc/display_compositor.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module cc.mojom;
 
 import "cc/ipc/frame_sink_id.mojom";
 import "cc/ipc/local_surface_id.mojom";
 import "cc/ipc/mojo_compositor_frame_sink.mojom";
 import "cc/ipc/surface_id.mojom";
@@ skipping 39 matching lines @@
       associated DisplayPrivate& display_private);
 
   // CreateOffscreenCompositorFrameSink is used by unprivileged clients.
   // An off screen CompositorFrameSink only submits frames to a buffer instead
   // of a display.
   CreateOffscreenCompositorFrameSink(
       cc.mojom.FrameSinkId frame_sink_id,
       cc.mojom.MojoCompositorFrameSink& compositor_frame_sink,
       cc.mojom.MojoCompositorFrameSinkPrivate& compositor_frame_sink_private,
       cc.mojom.MojoCompositorFrameSinkClient compositor_frame_sink_client);
+
+  // CreateOffscreenCanvasCompositorFrameSink is used by OffscreenCanvas.
+  CreateOffscreenCanvasCompositorFrameSink(

[Fady Samuel, 2017/02/21 14:16:18]

I don't think we should special case offscreen canvas. It should be no different
from any other client.

+      cc.mojom.FrameSinkId frame_sink_id,
+      cc.mojom.MojoCompositorFrameSink& compositor_frame_sink,
+      cc.mojom.MojoCompositorFrameSinkClient compositor_frame_sink_client);
+
 };
 
 // The DisplayCompositorClient interface is implemented by the Display
 // Compositor Host, a stable, and privileged peer service to the display
 // compositor. The display compositor host is either the browser process in
 // Chrome or the window server process.
 interface DisplayCompositorClient {
   // Called by the display compositor immediately upon receiving a
   // CompositorFrame with a new SurfaceId for the first time.
   OnSurfaceCreated(SurfaceInfo surface_info);
 };