CC Animation: Start replacing int layer_id with ElementId element_id.

cc/animation/animation_player.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_PLAYER_H_
 #define CC_ANIMATION_ANIMATION_PLAYER_H_
 
 #include <vector>
 
 #include "base/containers/linked_list.h"
@@ skipping 21 matching lines @@
 // same-property animations.
 // Each AnimationPlayer has its copy on the impl thread.
 // This is a CC counterpart for blink::AnimationPlayer (in 1:1 relationship).
 class CC_EXPORT AnimationPlayer : public base::RefCounted<AnimationPlayer>,
                                   public base::LinkNode<AnimationPlayer> {
  public:
   static scoped_refptr<AnimationPlayer> Create(int id);
   scoped_refptr<AnimationPlayer> CreateImplInstance() const;
 
   int id() const { return id_; }
-  int layer_id() const { return layer_id_; }
+  ElementId element_id() const { return element_id_; }
 
   // Parent AnimationHost. AnimationPlayer can be detached from
   // AnimationTimeline.
   AnimationHost* animation_host() { return animation_host_; }
   const AnimationHost* animation_host() const { return animation_host_; }
   void SetAnimationHost(AnimationHost* animation_host);
 
   // Parent AnimationTimeline.
   AnimationTimeline* animation_timeline() { return animation_timeline_; }
   const AnimationTimeline* animation_timeline() const {
     return animation_timeline_;
   }
   void SetAnimationTimeline(AnimationTimeline* timeline);
 
   // ElementAnimations object where this player is listed.
   scoped_refptr<ElementAnimations> element_animations() const {
     return element_animations_;
   }
 
   void set_layer_animation_delegate(AnimationDelegate* delegate) {
     layer_animation_delegate_ = delegate;
   }
 
-  void AttachLayer(int layer_id);
+  void AttachLayer(ElementId element_id);
   void DetachLayer();
 
   void AddAnimation(std::unique_ptr<Animation> animation);
   void PauseAnimation(int animation_id, double time_offset);
   void RemoveAnimation(int animation_id);
   void AbortAnimation(int animation_id);
   void AbortAnimations(TargetProperty::Type target_property,
                        bool needs_completion);
 
   void PushPropertiesTo(AnimationPlayer* player_impl);
@@ skipping 37 matching lines @@
   // to non-attached AnimationPlayers.
   std::vector<std::unique_ptr<Animation>> animations_;
 
   AnimationHost* animation_host_;
   AnimationTimeline* animation_timeline_;
   // element_animations isn't null if player attached to an element (layer).
   scoped_refptr<ElementAnimations> element_animations_;
   AnimationDelegate* layer_animation_delegate_;
 
   int id_;
-  int layer_id_;
+  ElementId element_id_;
 
   DISALLOW_COPY_AND_ASSIGN(AnimationPlayer);
 };
 
 }  // namespace cc
 
 #endif  // CC_ANIMATION_ANIMATION_PLAYER_H_