cc: Use Element Id to Record Animation Changes

cc/trees/layer_tree_impl.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_TREES_LAYER_TREE_IMPL_H_
 #define CC_TREES_LAYER_TREE_IMPL_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 492 matching lines @@
   scoped_refptr<SyncedElasticOverscroll> elastic_overscroll_;
 
   std::unique_ptr<OwnedLayerImplList> layers_;
   LayerImplMap layer_id_map_;
   LayerImplList layer_list_;
   // Set of layers that need to push properties.
   std::unordered_set<LayerImpl*> layers_that_should_push_properties_;
 
   std::unordered_map<ElementId, int, ElementIdHash> element_layers_map_;
 
-  std::unordered_map<int, float> opacity_animations_map_;
-  std::unordered_map<int, gfx::Transform> transform_animations_map_;
-  std::unordered_map<int, FilterOperations> filter_animations_map_;
+  std::unordered_map<ElementId, float, ElementIdHash> opacity_animations_map_;

[wkorman, 2017/03/20 21:59:57]

Thoughts on naming these xx_to_yy? We did that for recently added
PropertyTrees::element_id_to_xxx_node_index for example. It can make the calling
code easier to follow since it's more obvious what we're mapping from/to.

So here would be something like element_id_to_opacity, element_id_to_transform,
element_id_to_filter_ops.

+  std::unordered_map<ElementId, gfx::Transform, ElementIdHash>
+      transform_animations_map_;
+  std::unordered_map<ElementId, FilterOperations, ElementIdHash>
+      filter_animations_map_;
 
   // Maps from clip layer ids to scroll layer ids.  Note that this only includes
   // the subset of clip layers that act as scrolling containers.  (This is
   // derived from LayerImpl::scroll_clip_layer_ and exists to avoid O(n) walks.)
   std::unordered_map<int, int> clip_scroll_map_;
 
   // Maps scroll layer ids to scrollbar layer ids.  For each scroll layer, there
   // may be 1 or 2 scrollbar layers (for vertical and horizontal).  (This is
   // derived from ScrollbarLayerImplBase::scroll_layer_id_ and exists to avoid
   // O(n) walks.)
@@ skipping 42 matching lines @@
 
   std::unique_ptr<PendingPageScaleAnimation> pending_page_scale_animation_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_IMPL_H_