Fix a memory leak in the layer animator

ui/gfx/compositor/layer_animator.cc

Index: ui/gfx/compositor/layer_animator.cc
diff --git a/ui/gfx/compositor/layer_animator.cc b/ui/gfx/compositor/layer_animator.cc
index f98904cfd22c99c710f45b573da2cccc1e220266..a2008817ad4e5e39cca685b3439f590a059d7f03 100644
--- a/ui/gfx/compositor/layer_animator.cc
+++ b/ui/gfx/compositor/layer_animator.cc
@@ -393,9 +393,12 @@ void LayerAnimator::RemoveAllAnimationsWithACommonProperty(
 }
 
 void LayerAnimator::ImmediatelySetNewTarget(LayerAnimationSequence* sequence) {
+  // Ensure that sequence is disposed of when this function completes.
+  scoped_ptr<LayerAnimationSequence> to_dispose(sequence);
   const bool abort = false;
   RemoveAllAnimationsWithACommonProperty(sequence, abort);
-  scoped_ptr<LayerAnimationSequence> removed(RemoveAnimation(sequence));
+  LayerAnimationSequence* removed = RemoveAnimation(sequence);
+  DCHECK(removed == NULL || removed == sequence);
   sequence->Progress(sequence->duration(), delegate());
 }