Make all LayerAnimationElement::Create*Element return unique_ptr

ui/compositor/layer_animation_sequence.h

Index: ui/compositor/layer_animation_sequence.h
diff --git a/ui/compositor/layer_animation_sequence.h b/ui/compositor/layer_animation_sequence.h
index e050439da7eed4a7687f224b309596bb1448b05d..0d2c884baf32fcd99d25328cb8b818dcfe10abbc 100644
--- a/ui/compositor/layer_animation_sequence.h
+++ b/ui/compositor/layer_animation_sequence.h
@@ -41,7 +41,8 @@ class COMPOSITOR_EXPORT LayerAnimationSequence
  public:
   LayerAnimationSequence();
   // Takes ownership of the given element and adds it to the sequence.
-  explicit LayerAnimationSequence(LayerAnimationElement* element);
+  explicit LayerAnimationSequence(
+      std::unique_ptr<LayerAnimationElement> element);
   virtual ~LayerAnimationSequence();
 
   // Sets the start time for the animation. This must be called before the
@@ -90,7 +91,7 @@ class COMPOSITOR_EXPORT LayerAnimationSequence
 
   // Adds an element to the sequence. The sequences takes ownership of this
   // element.
-  void AddElement(LayerAnimationElement* element);
+  void AddElement(std::unique_ptr<LayerAnimationElement> element);
 
   // Sequences can be looped indefinitely.
   void set_is_cyclic(bool is_cyclic) { is_cyclic_ = is_cyclic; }
@@ -137,7 +138,7 @@ class COMPOSITOR_EXPORT LayerAnimationSequence
  private:
   friend class LayerAnimatorTestController;
 
-  typedef std::vector<linked_ptr<LayerAnimationElement> > Elements;
+  using Elements = std::vector<std::unique_ptr<LayerAnimationElement>>;
 
   FRIEND_TEST_ALL_PREFIXES(LayerAnimatorTest,
                            ObserverReleasedBeforeAnimationSequenceEnds);