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

content/common/gpu/gpu_command_buffer_stub.h

Index: content/common/gpu/gpu_command_buffer_stub.h
diff --git a/content/common/gpu/gpu_command_buffer_stub.h b/content/common/gpu/gpu_command_buffer_stub.h
index 6e6a039916d3b9443024c816d7e439a955d02615..8e8922607e91d28847041ffd6e2873ddf7e5c125 100644
--- a/content/common/gpu/gpu_command_buffer_stub.h
+++ b/content/common/gpu/gpu_command_buffer_stub.h
@@ -13,6 +13,7 @@
 
 #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"
@@ -80,7 +81,9 @@ class GpuCommandBufferStub
                     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,
@@ -133,6 +136,7 @@ class GpuCommandBufferStub
   scoped_ptr<gpu::CommandBufferService> command_buffer_;
   scoped_ptr<gpu::GpuScheduler> scheduler_;
   GpuWatchdog* watchdog_;
+  ScopedRunnableMethodFactory<GpuCommandBufferStub> task_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuCommandBufferStub);
 };