Added LayerAnimationObserver::OnLayerAnimationStarted() notification.

ui/compositor/layer_animation_observer.cc

 // Copyright (c) 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.
 
 #include "ui/compositor/layer_animation_observer.h"
 
 #include "ui/compositor/layer_animation_sequence.h"
 
 namespace ui {
 
 ////////////////////////////////////////////////////////////////////////////////
 // LayerAnimationObserver
 
 LayerAnimationObserver::LayerAnimationObserver() {
 }
 
 LayerAnimationObserver::~LayerAnimationObserver() {
   StopObserving();
 }
 
+void LayerAnimationObserver::OnLayerAnimationStarted(
+    LayerAnimationSequence* sequence) {}
+
 bool LayerAnimationObserver::RequiresNotificationWhenAnimatorDestroyed() const {
   return false;
 }
 
 void LayerAnimationObserver::OnAttachedToSequence(
     LayerAnimationSequence* sequence) {
 }
 
 void LayerAnimationObserver::OnDetachedFromSequence(
     LayerAnimationSequence* sequence) {
@@ skipping 125 matching lines @@
 ImplicitAnimationObserver::AnimationStatus
 ImplicitAnimationObserver::AnimationStatusForProperty(
     LayerAnimationElement::AnimatableProperty property) const {
   PropertyAnimationStatusMap::const_iterator iter =
       property_animation_status_.find(property);
   return iter == property_animation_status_.end() ? ANIMATION_STATUS_UNKNOWN :
       iter->second;
 }
 
 }  // namespace ui