[animations] Adds metrics for jank on selected layer animations

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 c48e91a6a8cb60ad1cf1062605cf61652f84acb4..2a414f30309a09a7501870c5d884c73007c82859 100644
--- a/ui/compositor/layer_animation_sequence.h
+++ b/ui/compositor/layer_animation_sequence.h
@@ -127,6 +127,9 @@ class COMPOSITOR_EXPORT LayerAnimationSequence
   // Called when the animator is destroyed.
   void OnAnimatorDestroyed();
 
+  // Sets |animation_metrics_reporter_| and passes it to all |elements_|.
+  void SetAnimationMetricsReporter(AnimationMetricsReporter* reporter);
+
   // The last_progressed_fraction of the element most recently progressed by
   // by this sequence. Returns 0.0 if no elements have been progressed.
   double last_progressed_fraction() const { return last_progressed_fraction_; }
@@ -191,6 +194,9 @@ class COMPOSITOR_EXPORT LayerAnimationSequence
   // element.
   double last_progressed_fraction_;
 
+  // Used to tag animation elements to obtain metrics of animation performance.
+  AnimationMetricsReporter* animation_metrics_reporter_;
+
   base::WeakPtrFactory<LayerAnimationSequence> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerAnimationSequence);