[cc]: Add a BeginMainFrameNotExpectedSoon signal and route it to the RendererScheduler.

cc/trees/thread_proxy.h

Index: cc/trees/thread_proxy.h
diff --git a/cc/trees/thread_proxy.h b/cc/trees/thread_proxy.h
index b4050bd1afa2495103e15f87cd215994fb175616..d1bd06bf584a6df89553d64fe4c1356eee3b1b0b 100644
--- a/cc/trees/thread_proxy.h
+++ b/cc/trees/thread_proxy.h
@@ -226,6 +226,7 @@ class CC_EXPORT ThreadProxy : public Proxy,
   base::TimeDelta CommitToActivateDurationEstimate() override;
   void DidBeginImplFrameDeadline() override;
   void SendBeginFramesToChildren(const BeginFrameArgs& args) override;
+  void SendBeginMainFrameNoLongerRequired() override;
 
   // ResourceUpdateControllerClient implementation
   void ReadyToFinalizeTextureUpdates() override;
@@ -243,6 +244,7 @@ class CC_EXPORT ThreadProxy : public Proxy,
       const RendererCapabilities& capabilities);
   void BeginMainFrame(
       scoped_ptr<BeginMainFrameAndCommitState> begin_main_frame_state);
+  void BeginMainFrameNoLongerRequired();
   void DidCommitAndDrawFrame();
   void DidCompleteSwapBuffers();
   void SetAnimationEvents(scoped_ptr<AnimationEventsVector> queue);