Revert of Use element id's for animations

cc/animation/animation_player.cc

 // 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.
 
 #include "cc/animation/animation_player.h"
 
 #include <algorithm>
 
 #include "cc/animation/animation_delegate.h"
 #include "cc/animation/animation_host.h"
 #include "cc/animation/animation_timeline.h"
 #include "cc/animation/element_animations.h"
 
 namespace cc {
 
 scoped_refptr<AnimationPlayer> AnimationPlayer::Create(int id) {
   return make_scoped_refptr(new AnimationPlayer(id));
 }
 
 AnimationPlayer::AnimationPlayer(int id)
     : animation_host_(),
       animation_timeline_(),
       element_animations_(),
       animation_delegate_(),
-      id_(id) {
+      id_(id),
+      element_id_(0) {
   DCHECK(id_);
 }
 
 AnimationPlayer::~AnimationPlayer() {
   DCHECK(!animation_timeline_);
   DCHECK(!element_animations_);
 }
 
 scoped_refptr<AnimationPlayer> AnimationPlayer::CreateImplInstance() const {
   scoped_refptr<AnimationPlayer> player = AnimationPlayer::Create(id());
@@ skipping 14 matching lines @@
     UnregisterPlayer();
 
   animation_timeline_ = timeline;
 
   // Register player only if layer AND host attached.
   if (element_id_ && animation_host_)
     RegisterPlayer();
 }
 
 void AnimationPlayer::AttachElement(ElementId element_id) {
-  DCHECK(!element_id_);
+  DCHECK_EQ(element_id_, 0);
   DCHECK(element_id);
 
   element_id_ = element_id;
 
   // Register player only if layer AND host attached.
   if (animation_host_)
     RegisterPlayer();
 }
 
 void AnimationPlayer::DetachElement() {
   DCHECK(element_id_);
 
   if (animation_host_)
     UnregisterPlayer();
 
-  element_id_ = ElementId();
+  element_id_ = 0;
 }
 
 void AnimationPlayer::RegisterPlayer() {
   DCHECK(element_id_);
   DCHECK(animation_host_);
   DCHECK(!element_animations_);
 
   // Create ElementAnimations or re-use existing.
   animation_host_->RegisterPlayerForElement(element_id_, this);
   // Get local reference to shared ElementAnimations.
@@ skipping 133 matching lines @@
   }
 }
 
 void AnimationPlayer::SetNeedsCommit() {
   DCHECK(animation_host_);
   animation_host_->SetNeedsCommit();
   animation_host_->SetNeedsRebuildPropertyTrees();
 }
 
 }  // namespace cc