compositor/layer_animator: handle delegate removal in LayerAnimation::StopAnimating

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 39585a7c946e5a7656d46f02739826e1754e8a69..adff73fe89afe1be63b1d5f930a468b9f5be4d9f 100644
--- a/ui/compositor/layer_animator.cc
+++ b/ui/compositor/layer_animator.cc
@@ -409,7 +409,7 @@ void LayerAnimator::Step(base::TimeTicks now) {
 
 void LayerAnimator::StopAnimatingInternal(bool abort) {
   scoped_refptr<LayerAnimator> retain(this);
-  while (is_animating()) {
+  while (is_animating() && delegate()) {
     // We're going to attempt to finish the first running animation. Let's
     // ensure that it's valid.
     PurgeDeletedAnimations();
@@ -517,6 +517,8 @@ void LayerAnimator::FinishAnimation(
     sequence->Abort(delegate());
   else
     ProgressAnimationToEnd(sequence);
+  if (!delegate())
+    return;
   ProcessQueue();
   UpdateAnimationState();
 }