CC Animation: Make LayerAnimationController to have just one event observer.

cc/animation/element_animations.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/element_animations.h"
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "cc/animation/animation_host.h"
 #include "cc/animation/animation_player.h"
@@ skipping 125 matching lines @@
 
 Animation* ElementAnimations::GetAnimation(
     TargetProperty::Type target_property) const {
   return layer_animation_controller_->GetAnimation(target_property);
 }
 
 Animation* ElementAnimations::GetAnimationById(int animation_id) const {
   return layer_animation_controller_->GetAnimationById(animation_id);
 }
 
-void ElementAnimations::AddEventObserver(
+void ElementAnimations::SetEventObserver(
     LayerAnimationEventObserver* observer) {
-  layer_animation_controller_->AddEventObserver(observer);
-}
-
-void ElementAnimations::RemoveEventObserver(
-    LayerAnimationEventObserver* observer) {
-  layer_animation_controller_->RemoveEventObserver(observer);
+  layer_animation_controller_->SetEventObserver(observer);
 }
 
 void ElementAnimations::OnFilterAnimated(LayerTreeType tree_type,
                                          const FilterOperations& filters) {
   DCHECK(layer_id());
   DCHECK(animation_host());
   DCHECK(animation_host()->mutator_host_client());
   animation_host()->mutator_host_client()->SetLayerFilterMutated(
       layer_id(), tree_type, filters);
 }
@@ skipping 119 matching lines @@
   if (animation_host()) {
     DCHECK(animation_host()->mutator_host_client());
     return animation_host()->mutator_host_client()->GetScrollOffsetForAnimation(
         layer_id());
   }
 
   return gfx::ScrollOffset();
 }
 
 }  // namespace cc