[ash-md] Enhanced LayerAnimator to allow animations to be aborted/started in OnLayerAnimationStarte…

ui/compositor/layer_animator.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_animator.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 828 matching lines @@
   LayerAnimatorCollection* collection = GetLayerAnimatorCollection();
   if (is_animating() || adding_animations_)
     start_time = last_step_time_;
   else if (collection && collection->HasActiveAnimators())
     start_time = collection->last_tick_time();
   else
     start_time = base::TimeTicks::Now();
 
   if (!sequence->animation_group_id())
     sequence->set_animation_group_id(cc::AnimationIdProvider::NextGroupId());
-  if (!sequence->waiting_for_group_start() ||
-      sequence->IsFirstElementThreaded()) {
-    sequence->set_start_time(start_time);
-    sequence->Start(delegate());
-  }
+
   running_animations_.push_back(
       RunningAnimation(sequence->AsWeakPtr()));
 
   // Need to keep a reference to the animation.
   AddToQueueIfNotPresent(sequence);
 
+  if (!sequence->waiting_for_group_start() ||
+      sequence->IsFirstElementThreaded()) {
+    sequence->set_start_time(start_time);
+    sequence->Start(delegate());
+  }
+
   // Ensure that animations get stepped at their start time.
   Step(start_time);
 
   return true;
 }
 
 void LayerAnimator::GetTargetValue(
     LayerAnimationElement::TargetValue* target) const {
   for (AnimationQueue::const_iterator iter = animation_queue_.begin();
        iter != animation_queue_.end(); ++iter) {
@@ skipping 59 matching lines @@
     const base::WeakPtr<LayerAnimationSequence>& sequence)
     : sequence_(sequence) {
 }
 
 LayerAnimator::RunningAnimation::RunningAnimation(
     const RunningAnimation& other) = default;
 
 LayerAnimator::RunningAnimation::~RunningAnimation() { }
 
 }  // namespace ui