Reintroduce OffscreenCanvasSurfaceClient interface.

third_party/WebKit/public/platform/modules/offscreencanvas/offscreen_canvas_surface.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 blink.mojom;
 
 import "cc/ipc/frame_sink_id.mojom";
 import "cc/ipc/frame_sink_manager.mojom";
 import "cc/ipc/mojo_compositor_frame_sink.mojom";
 import "cc/ipc/surface_id.mojom";
+import "cc/ipc/surface_info.mojom";
 import "cc/ipc/surface_sequence.mojom";
 
 interface OffscreenCanvasSurface {
   Require(cc.mojom.SurfaceId surface_id, cc.mojom.SurfaceSequence sequence);
   Satisfy(cc.mojom.SurfaceSequence sequence);
 };
 
+interface OffscreenCanvasSurfaceClient {
+  OnSurfaceCreated(cc.mojom.SurfaceInfo surface_info);
+};
+
 // Creates OffscreenCanvasSurface and MojoCompositorFrameSink instances for use
 // with offscreen canvas.
 interface OffscreenCanvasProvider {
-  // TODO(kylechar): Observer interface shouldn't be FrameSinkManagerClient.
   // Create an OffscreenCanvasSurface for |frame_sink_id|. |client| will observe
   // any changes to the SurfaceId associated with |frame_sink_id|.
   CreateOffscreenCanvasSurface(cc.mojom.FrameSinkId parent_frame_sink_id,
                                cc.mojom.FrameSinkId frame_sink_id,
-                               cc.mojom.FrameSinkManagerClient client,
+                               OffscreenCanvasSurfaceClient client,
                                OffscreenCanvasSurface& surface);
 
   // Create an MojoCompositorFrameSink for |frame_sink_id|. This must happen
   // after creating an OffsreenCanvasSurface for |frame_sink_id|.
   CreateCompositorFrameSink(cc.mojom.FrameSinkId frame_sink_id,
                             cc.mojom.MojoCompositorFrameSinkClient client,
                             cc.mojom.MojoCompositorFrameSink& sink);
 };