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

gpu/command_buffer/service/gpu_scheduler.h

Index: gpu/command_buffer/service/gpu_scheduler.h
diff --git a/gpu/command_buffer/service/gpu_scheduler.h b/gpu/command_buffer/service/gpu_scheduler.h
index 173e953b1fdacfbb881a4185b63c13dbc141a8f7..7420268d62f475ab04b7a9f42301ded689030113 100644
--- a/gpu/command_buffer/service/gpu_scheduler.h
+++ b/gpu/command_buffer/service/gpu_scheduler.h
@@ -61,7 +61,7 @@ class GpuScheduler : public CommandBufferEngine {
   void Destroy();
   void DestroyCommon();
 
-  virtual void ProcessCommands();
+  void PutChanged(bool sync);
 
   // Helper which causes a call to ProcessCommands to be scheduled later.
   void ScheduleProcessCommands();
@@ -105,14 +105,14 @@ class GpuScheduler : public CommandBufferEngine {
 
   // Sets a callback that is called when a glResizeCHROMIUM command
   // is processed.
-  virtual void SetResizeCallback(Callback1<gfx::Size>::Type* callback);
+  void SetResizeCallback(Callback1<gfx::Size>::Type* callback);
 
   // Sets a callback which is called when a SwapBuffers command is processed.
   // Must be called after Initialize().
   // It is not defined on which thread this callback is called.
-  virtual void SetSwapBuffersCallback(Callback0::Type* callback);
+  void SetSwapBuffersCallback(Callback0::Type* callback);
 
-  virtual void SetCommandProcessedCallback(Callback0::Type* callback);
+  void SetCommandProcessedCallback(Callback0::Type* callback);
 
   // Sets a callback which is called after a Set/WaitLatch command is processed.
   // The bool parameter will be true for SetLatch, and false for a WaitLatch
@@ -139,7 +139,8 @@ class GpuScheduler : public CommandBufferEngine {
  private:
   // Called via a callback just before we are supposed to call the
   // user's swap buffers callback.
-  virtual void WillSwapBuffers();
+  void WillSwapBuffers();
+  void ProcessCommands();
 
   // The GpuScheduler holds a weak reference to the CommandBuffer. The
   // CommandBuffer owns the GpuScheduler and holds a strong reference to it