Plumb GpuSwapBuffers completion from Mus GPU thread to WS thread

components/mus/gles2/command_buffer_local_client.h

 // Copyright 2015 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 COMPONENTS_MUS_GLES2_COMMAND_BUFFER_LOCAL_CLIENT_H_
 #define COMPONENTS_MUS_GLES2_COMMAND_BUFFER_LOCAL_CLIENT_H_
 
 #include <stdint.h>
 
+#include "ui/gfx/swap_result.h"
+
 namespace mus {
 
 class CommandBufferLocalClient {
  public:
   virtual void UpdateVSyncParameters(int64_t timebase, int64_t interval) = 0;
   virtual void DidLoseContext() = 0;
+  virtual void GpuCompletedSwapBuffers(gfx::SwapResult result) = 0;
 
  protected:
   virtual ~CommandBufferLocalClient() {}
 };
 
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_GLES2_COMMAND_BUFFER_LOCAL_CLIENT_H_