cc : Track opacity animation changes on effect tree

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 935f4f01a92a60492d2c87cea6345e3e28ab10c3..418ca7d8ad7d29328f02d21df47654e26386d57c 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -280,6 +280,10 @@ class CC_EXPORT LayerTreeHostImpl
       ElementId element_id,
       ElementListType list_type,
       bool is_animating) override;
+  void ElementOpacityIsAnimatingChanged(ElementId element_id,
+                                        ElementListType list_type,
+                                        AnimationChangeType change_type,
+                                        bool is_animating) override;
   void ScrollOffsetAnimationFinished() override;
   gfx::ScrollOffset GetScrollOffsetForAnimation(
       ElementId element_id) const override;