cc: Allow the main thread to cancel commits

cc/test/layer_tree_test.h

Index: cc/test/layer_tree_test.h
diff --git a/cc/test/layer_tree_test.h b/cc/test/layer_tree_test.h
index 4e4f9510d2e67b4fb55495221d728b4dfc8cc9af..248e150aeb3e59ffe0b163575257a0c442e793bf 100644
--- a/cc/test/layer_tree_test.h
+++ b/cc/test/layer_tree_test.h
@@ -52,11 +52,13 @@ class TestHooks : public AnimationDelegate {
   virtual void ApplyScrollAndScale(gfx::Vector2d scroll_delta,
                                    float scale) {}
   virtual void Animate(base::TimeTicks monotonic_time) {}
+  virtual void WillBeginFrame() {}
   virtual void Layout() {}
   virtual void DidInitializeOutputSurface(bool succeeded) {}
   virtual void DidFailToInitializeOutputSurface() {}
   virtual void DidAddAnimation() {}
   virtual void DidCommit() {}
+  virtual void WillCommit() {}
   virtual void DidCommitAndDrawFrame() {}
   virtual void DidCompleteSwapBuffers() {}
   virtual void ScheduleComposite() {}