CC Animation: Make ElementAnimations a ref-counted object.

cc/animation/animation_host.h

 // Copyright 2015 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_ANIMATION_ANIMATION_HOST_H_
 #define CC_ANIMATION_ANIMATION_HOST_H_
 
 #include <memory>
 #include <unordered_map>
 
@@ skipping 43 matching lines @@
   AnimationTimeline* GetTimelineById(int timeline_id) const;
 
   void ClearTimelines();
 
   void RegisterLayer(int layer_id, LayerTreeType tree_type);
   void UnregisterLayer(int layer_id, LayerTreeType tree_type);
 
   void RegisterPlayerForLayer(int layer_id, AnimationPlayer* player);
   void UnregisterPlayerForLayer(int layer_id, AnimationPlayer* player);
 
-  ElementAnimations* GetElementAnimationsForLayerId(int layer_id) const;
+  scoped_refptr<ElementAnimations> GetElementAnimationsForLayerId(
+      int layer_id) const;
 
   // TODO(loyso): Get rid of LayerAnimationController.
   LayerAnimationController* GetControllerForLayerId(int layer_id) const;
 
   // Parent LayerTreeHost or LayerTreeHostImpl.
   MutatorHostClient* mutator_host_client() { return mutator_host_client_; }
   const MutatorHostClient* mutator_host_client() const {
     return mutator_host_client_;
   }
   void SetMutatorHostClient(MutatorHostClient* client);
@@ skipping 97 matching lines @@
 
  private:
   explicit AnimationHost(ThreadInstance thread_instance);
 
   void PushTimelinesToImplThread(AnimationHost* host_impl) const;
   void RemoveTimelinesFromImplThread(AnimationHost* host_impl) const;
   void PushPropertiesToImplThread(AnimationHost* host_impl);
 
   void EraseTimeline(scoped_refptr<AnimationTimeline> timeline);
 
-  // TODO(loyso): For now AnimationPlayers share LayerAnimationController object
-  // if they are attached to the same element(layer). Note that Element can
-  // contain many Layers.
+  // AnimationPlayers share ElementAnimations object if they are attached to the
+  // same element(layer). Note that Element can contain many Layers.
   using LayerToElementAnimationsMap =
-      std::unordered_map<int, std::unique_ptr<ElementAnimations>>;
+      std::unordered_map<int, scoped_refptr<ElementAnimations>>;
   LayerToElementAnimationsMap layer_to_element_animations_map_;
 
   // A list of all timelines which this host owns.
   using IdToTimelineMap =
       std::unordered_map<int, scoped_refptr<AnimationTimeline>>;
   IdToTimelineMap id_to_timeline_map_;
 
   AnimationControllerMap active_animation_controllers_;
   AnimationControllerMap all_animation_controllers_;
 
   MutatorHostClient* mutator_host_client_;
 
   class ScrollOffsetAnimations;
   std::unique_ptr<ScrollOffsetAnimations> scroll_offset_animations_;
 
   const ThreadInstance thread_instance_;
 
   bool supports_scroll_animations_;
 
   DISALLOW_COPY_AND_ASSIGN(AnimationHost);
 };
 
 }  // namespace cc
 
 #endif  // CC_ANIMATION_ANIMATION_HOST_H_