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

gpu/command_buffer/common/command_buffer_mock.h

Index: gpu/command_buffer/common/command_buffer_mock.h
diff --git a/gpu/command_buffer/common/command_buffer_mock.h b/gpu/command_buffer/common/command_buffer_mock.h
index 8281f7f39e2488ecce94b21e9f24b18572fd868c..4da8e82d4dc51f3ec9835111acab1ac711579c7a 100644
--- a/gpu/command_buffer/common/command_buffer_mock.h
+++ b/gpu/command_buffer/common/command_buffer_mock.h
@@ -26,7 +26,7 @@ class MockCommandBuffer : public CommandBuffer {
   MOCK_METHOD0(GetRingBuffer, Buffer());
   MOCK_METHOD0(GetState, State());
   MOCK_METHOD1(Flush, void(int32 put_offset));
-  MOCK_METHOD1(FlushSync, State(int32 put_offset));
+  MOCK_METHOD2(FlushSync, State(int32 put_offset, int32 last_known_get));
   MOCK_METHOD1(SetGetOffset, void(int32 get_offset));
   MOCK_METHOD2(CreateTransferBuffer, int32(size_t size, int32 id_request));
   MOCK_METHOD1(DestroyTransferBuffer, void(int32 handle));