Rework FlushSync to return early if commands have been processed since the last update

content/common/gpu/gpu_command_buffer_stub.h

 // Copyright (c) 2011 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_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_
 #define CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_
 #pragma once
 
 #if defined(ENABLE_GPU)
 
 #include <vector>
 #include <string>
 
 #include "base/memory/weak_ptr.h"
 #include "base/process.h"
+#include "base/task.h"
 #include "gpu/command_buffer/service/command_buffer_service.h"
 #include "gpu/command_buffer/service/gpu_scheduler.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_message.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/size.h"
 
 class GpuChannel;
 class GpuWatchdog;
 
@@ skipping 47 matching lines @@
   void AcceleratedSurfaceBuffersSwapped(uint64 swap_buffers_count);
 #endif  // defined(OS_MACOSX)
 
  private:
   // Message handlers:
   void OnInitialize(base::SharedMemoryHandle ring_buffer,
                     int32 size,
                     bool* result);
   void OnGetState(gpu::CommandBuffer::State* state);
   void OnAsyncGetState();
-  void OnFlush(int32 put_offset, gpu::CommandBuffer::State* state);
+  void OnFlush(int32 put_offset,
+               int32 last_known_get,
+               gpu::CommandBuffer::State* state);
   void OnAsyncFlush(int32 put_offset);
   void OnCreateTransferBuffer(int32 size, int32 id_request, int32* id);
   void OnRegisterTransferBuffer(base::SharedMemoryHandle transfer_buffer,
                                 size_t size,
                                 int32 id_request,
                                 int32* id);
   void OnDestroyTransferBuffer(int32 id);
   void OnGetTransferBuffer(int32 id,
                            base::SharedMemoryHandle* transfer_buffer,
                            uint32* size);
@@ skipping 32 matching lines @@
 #endif  // defined(OS_WIN)
 
   // The following two fields are used on Mac OS X to identify the window
   // for the rendering results on the browser side.
   int32 renderer_id_;
   int32 render_view_id_;
 
   scoped_ptr<gpu::CommandBufferService> command_buffer_;
   scoped_ptr<gpu::GpuScheduler> scheduler_;
   GpuWatchdog* watchdog_;
+  ScopedRunnableMethodFactory<GpuCommandBufferStub> task_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuCommandBufferStub);
 };
 
 #endif  // defined(ENABLE_GPU)
 
 #endif  // CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_