cc: Use Element Id to Record Animation Changes

cc/trees/property_tree.cc

Index: cc/trees/property_tree.cc
diff --git a/cc/trees/property_tree.cc b/cc/trees/property_tree.cc
index da62e3e319d7d33972852715925288622cc85f37..5733ef658d32ac72a573af0a431e9ded2fb19653 100644
--- a/cc/trees/property_tree.cc
+++ b/cc/trees/property_tree.cc
@@ -178,6 +178,14 @@ bool TransformTree::ComputeTranslation(int source_id,
   return true;
 }
 
+TransformNode* TransformTree::FindNodeFromElementId(ElementId id) {
+  auto iterator = property_trees()->element_id_to_transform_node_index.find(id);
+  if (iterator == property_trees()->element_id_to_transform_node_index.end())
+    return nullptr;
+
+  return Node(iterator->second);
+}
+
 void TransformTree::OnTransformAnimated(const gfx::Transform& transform,
                                         int id,
                                         LayerTreeImpl* layer_tree_impl) {
@@ -849,6 +857,14 @@ void EffectTree::UpdateSurfaceContentsScale(EffectNode* effect_node) {
           transform_tree.ToScreen(transform_node->id), layer_scale_factor);
 }
 
+EffectNode* EffectTree::FindNodeFromElementId(ElementId id) {
+  auto iterator = property_trees()->element_id_to_effect_node_index.find(id);
+  if (iterator == property_trees()->element_id_to_effect_node_index.end())
+    return nullptr;
+
+  return Node(iterator->second);
+}
+
 void EffectTree::OnOpacityAnimated(float opacity,
                                    int id,
                                    LayerTreeImpl* layer_tree_impl) {