cc: Introduce BeginFrame sequence numbers and acknowledgements.

content/browser/compositor/mus_browser_compositor_output_surface.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_COMPOSITOR_MUS_BROWSER_COMPOSITOR_OUTPUT_SURFACE_H_
 #define CONTENT_BROWSER_COMPOSITOR_MUS_BROWSER_COMPOSITOR_OUTPUT_SURFACE_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 40 matching lines @@
   MusBrowserCompositorOutputSurface(
       aura::Window* window,
       scoped_refptr<ContextProviderCommandBuffer> context,
       gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager,
       const UpdateVSyncParametersCallback& update_vsync_parameters_callback,
       std::unique_ptr<display_compositor::CompositorOverlayCandidateValidator>
           overlay_candidate_validator);
 
   ~MusBrowserCompositorOutputSurface() override;
 
+  cc::BeginFrameSource* GetBeginFrameSource();
+
  protected:
   // cc::OutputSurface implementation.
   void SwapBuffers(cc::OutputSurfaceFrame frame) override;
 
   // cc::CompositorFrameSinkClient:
   void SetBeginFrameSource(cc::BeginFrameSource* source) override;
   void ReclaimResources(const cc::ReturnedResourceArray& resources) override;
   void SetTreeActivationCallback(const base::Closure& callback) override;
   void DidReceiveCompositorFrameAck() override;
   void DidLoseCompositorFrameSink() override;
@@ skipping 11 matching lines @@
   const gpu::Mailbox& GetMailboxFromResourceId(uint32_t id);
 
   // TODO(mfomitchev): Remove once we complete the switch to Aura-Mus.
   ui::Window* ui_window_;
   std::unique_ptr<ui::WindowCompositorFrameSink> ui_compositor_frame_sink_;
 
   aura::Window* window_;
   std::unique_ptr<aura::WindowCompositorFrameSink> compositor_frame_sink_;
   std::vector<uint32_t> free_resource_ids_;
   std::vector<gpu::Mailbox> mailboxes_;
+  cc::BeginFrameSource* begin_frame_source_;
 
   DISALLOW_COPY_AND_ASSIGN(MusBrowserCompositorOutputSurface);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_COMPOSITOR_MUS_BROWSER_COMPOSITOR_OUTPUT_SURFACE_H_