cc: Introduce BeginFrame sequence numbers and acknowledgements.

content/browser/renderer_host/offscreen_canvas_compositor_frame_sink.h

 // 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_OFFSCREEN_CANVAS_COMPOSITOR_FRAME_SINK_H_
 #define CONTENT_BROWSER_RENDERER_HOST_OFFSCREEN_CANVAS_COMPOSITOR_FRAME_SINK_H_
 
 #include "cc/surfaces/surface_factory.h"
 #include "cc/surfaces/surface_factory_client.h"
 #include "third_party/WebKit/public/platform/modules/offscreencanvas/offscreen_canvas_surface.mojom.h"
@@ skipping 11 matching lines @@
 
   static void Create(const cc::SurfaceId& surface_id,
                      cc::mojom::MojoCompositorFrameSinkClientPtr client,
                      cc::mojom::MojoCompositorFrameSinkRequest request);
 
   // cc::mojom::MojoCompositorFrameSink implementation.
   void SubmitCompositorFrame(const cc::LocalFrameId& local_frame_id,
                              cc::CompositorFrame frame) override;
   void SetNeedsBeginFrame(bool needs_begin_frame) override;
   void EvictFrame() override;
+  void BeginFrameDidNotDraw(const cc::BeginFrameAck& ack) override;
 
   // cc::SurfaceFactoryClient implementation.
   void ReturnResources(const cc::ReturnedResourceArray& resources) override;
   void WillDrawSurface(const cc::LocalFrameId& id,
                        const gfx::Rect& damage_rect) override;
   void SetBeginFrameSource(cc::BeginFrameSource* begin_frame_source) override;
 
  private:
   void DidReceiveCompositorFrameAck();
 
   cc::SurfaceId surface_id_;
   std::unique_ptr<cc::SurfaceFactory> surface_factory_;
   cc::mojom::MojoCompositorFrameSinkClientPtr client_;
   int ack_pending_count_ = 0;
   cc::ReturnedResourceArray surface_returned_resources_;
 
   DISALLOW_COPY_AND_ASSIGN(OffscreenCanvasCompositorFrameSink);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_OFFSCREEN_CANVAS_COMPOSITOR_FRAME_SINK_H_