cc: LayerTreeHostImpl uses element id to tick animations

cc/trees/layer_tree_impl.h

Index: cc/trees/layer_tree_impl.h
diff --git a/cc/trees/layer_tree_impl.h b/cc/trees/layer_tree_impl.h
index d34a1998f2ffed02ddb50639c0ed2875177c283a..2f178a7662e334e89a49bc07fb6d0b2798b6ad94 100644
--- a/cc/trees/layer_tree_impl.h
+++ b/cc/trees/layer_tree_impl.h
@@ -145,9 +145,15 @@ class CC_EXPORT LayerTreeImpl {
   LayerImplList::reverse_iterator rbegin();
   LayerImplList::reverse_iterator rend();
 
+  // TODO(crbug.com/702832): This won't be needed if overlay scrollbars have
+  // element ids.
   void AddToOpacityAnimationsMap(int id, float opacity);
-  void AddToTransformAnimationsMap(int id, gfx::Transform transform);
-  void AddToFilterAnimationsMap(int id, const FilterOperations& filters);
+
+  void SetTreeLayerTransformMutated(ElementId element_id,
+                                    const gfx::Transform& transform);
+  void SetTreeLayerOpacityMutated(ElementId element_id, float opacity);
+  void SetTreeLayerFilterMutated(ElementId element_id,

[ajuma, 2017/03/21 22:00:30]

Wdyt of removing 'TreeLayer' from these names since they just involve property
trees rather than layers now?

[weiliangc, 2017/03/22 18:44:15]

Done.

+                                 const FilterOperations& filters);
 
   int source_frame_number() const { return source_frame_number_; }
   void set_source_frame_number(int frame_number) {