Limit outstanding surface draw swaps to max_frames_pending.

cc/surfaces/display_client.h

Index: cc/surfaces/display_client.h
diff --git a/cc/surfaces/display_client.h b/cc/surfaces/display_client.h
index 6134bf5fc20430f986941a81b2d588635092b5d7..0c5f3ccfa05a0cb8af02b7a5b35846ef81096854 100644
--- a/cc/surfaces/display_client.h
+++ b/cc/surfaces/display_client.h
@@ -15,6 +15,8 @@ class DisplayClient {
  public:
   virtual scoped_ptr<OutputSurface> CreateOutputSurface() = 0;
   virtual void DisplayDamaged() = 0;
+  virtual void DidSwapBuffers() = 0;
+  virtual void DidSwapBuffersComplete() = 0;
 
  protected:
   virtual ~DisplayClient() {}