[ash-md] Enhanced LayerAnimator to allow animations to be aborted/started in OnLayerAnimationStarte…

ui/compositor/layer_animation_observer.h

Index: ui/compositor/layer_animation_observer.h
diff --git a/ui/compositor/layer_animation_observer.h b/ui/compositor/layer_animation_observer.h
index cd5747926d409c0f77aa7ec1cd839aeaf67b12d1..b83acde04fb09c4e8591dcf7f214cec258505081 100644
--- a/ui/compositor/layer_animation_observer.h
+++ b/ui/compositor/layer_animation_observer.h
@@ -15,6 +15,7 @@
 namespace ui {
 
 namespace test {
+class CountCheckingLayerAnimationObserver;
 class LayerAnimationObserverTestApi;
 }  // namespace test
 
@@ -81,6 +82,7 @@ class COMPOSITOR_EXPORT LayerAnimationObserver  {
 
  private:
   friend class LayerAnimationSequence;
+  friend class test::CountCheckingLayerAnimationObserver;
   friend class test::LayerAnimationObserverTestApi;
 
   // Called when |this| is added to |sequence|'s observer list.