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

ui/compositor/layer_animator.cc

Index: ui/compositor/layer_animator.cc
diff --git a/ui/compositor/layer_animator.cc b/ui/compositor/layer_animator.cc
index 87b852ecf93b2557040aa3e19334af0e5cbacf1c..72ca40d0424c3994295773506ccc828c22867c6a 100644
--- a/ui/compositor/layer_animator.cc
+++ b/ui/compositor/layer_animator.cc
@@ -846,17 +846,19 @@ bool LayerAnimator::StartSequenceImmediately(LayerAnimationSequence* sequence) {
 
   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);