cc: Handle retroactive BeginFrames in the Scheduler.

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 a494da340a8a12add7c1505eced073805ed71176..d525c794047d4408f7e3caa85195a97a52ba4026 100644
--- a/cc/trees/thread_proxy.h
+++ b/cc/trees/thread_proxy.h
@@ -76,7 +76,7 @@ class ThreadProxy : public Proxy,
   virtual void DidLoseOutputSurfaceOnImplThread() OVERRIDE;
   virtual void DidSwapBuffersOnImplThread() OVERRIDE {}
   virtual void OnSwapBuffersCompleteOnImplThread() OVERRIDE;
-  virtual void BeginImplFrame(const BeginFrameArgs& args) OVERRIDE;
+  virtual void BeginFrame(const BeginFrameArgs& args) OVERRIDE;
   virtual void OnCanDrawStateChanged(bool can_draw) OVERRIDE;
   virtual void NotifyReadyToActivate() OVERRIDE;
   // Please call these 2 functions through
@@ -101,7 +101,8 @@ class ThreadProxy : public Proxy,
   virtual void DidManageTiles() OVERRIDE;
 
   // SchedulerClient implementation
-  virtual void SetNeedsBeginImplFrame(bool enable) OVERRIDE;
+  virtual void SetNeedsBeginFrame(bool enable) OVERRIDE;
+  virtual void WillBeginImplFrame(const BeginFrameArgs& args) OVERRIDE;
   virtual void ScheduledActionSendBeginMainFrame() OVERRIDE;
   virtual DrawSwapReadbackResult ScheduledActionDrawAndSwapIfPossible()
       OVERRIDE;