Revert of Use element id's for 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 a92ad895522ecea617ba7b2574c0ffd67ab85b31..5f7ab9dd90931ce83c2157ca01220d6836a8d822 100644
--- a/cc/trees/layer_tree_impl.h
+++ b/cc/trees/layer_tree_impl.h
@@ -153,9 +153,20 @@
   LayerListReverseIterator<LayerImpl> rbegin();
   LayerListReverseIterator<LayerImpl> rend();
 
+  struct CC_EXPORT ElementLayers {
+    // Transform and opacity mutations apply to this layer.
+    LayerImpl* main = nullptr;
+    // Scroll mutations apply to this layer.
+    LayerImpl* scroll = nullptr;
+  };
+
+  void AddToElementMap(LayerImpl* layer);
+  void RemoveFromElementMap(LayerImpl* layer);
+
   void AddToOpacityAnimationsMap(int id, float opacity);
   void AddToTransformAnimationsMap(int id, gfx::Transform transform);
 
+  ElementLayers GetMutableLayers(uint64_t element_id);
   int source_frame_number() const { return source_frame_number_; }
   void set_source_frame_number(int frame_number) {
     source_frame_number_ = frame_number;
@@ -253,8 +264,6 @@
     return top_controls_shown_ratio_.get();
   }
 
-  void SetElementIdsForTesting();
-
   // Updates draw properties and render surface layer list, as well as tile
   // priorities. Returns false if it was unable to update.  Updating lcd
   // text may cause invalidations, so should only be done after a commit.
@@ -296,13 +305,6 @@
   gfx::Rect RootScrollLayerDeviceViewportBounds() const;
 
   LayerImpl* LayerById(int id) const;
-
-  // TODO(vollick): this is deprecated. It is used by
-  // animation/compositor-worker to look up layers to mutate, but in future, we
-  // will update property trees.
-  LayerImpl* LayerByElementId(ElementId element_id) const;
-  void AddToElementMap(LayerImpl* layer);
-  void RemoveFromElementMap(LayerImpl* layer);
 
   void AddLayerShouldPushProperties(LayerImpl* layer);
   void RemoveLayerShouldPushProperties(LayerImpl* layer);
@@ -521,7 +523,7 @@
   // Set of layers that need to push properties.
   std::unordered_set<LayerImpl*> layers_that_should_push_properties_;
 
-  std::unordered_map<ElementId, LayerImpl*, ElementIdHash> element_layers_map_;
+  std::unordered_map<uint64_t, ElementLayers> element_layers_map_;
 
   std::unordered_map<int, float> opacity_animations_map_;
   std::unordered_map<int, gfx::Transform> transform_animations_map_;