Adds UMA for screen rotation animation smoothness.

ash/rotator/screen_rotation_animator.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_ROTATOR_SCREEN_ROTATION_ANIMATOR_H_
 #define ASH_ROTATOR_SCREEN_ROTATION_ANIMATOR_H_
 
 #include <stdint.h>
 
 #include "ash/ash_export.h"
@@ skipping 31 matching lines @@
   void Rotate(display::Display::Rotation new_rotation,
               display::Display::RotationSource source);
 
   int64_t display_id() const { return display_id_; }
 
   void AddScreenRotationAnimatorObserver(
       ScreenRotationAnimatorObserver* observer);
   void RemoveScreenRotationAnimatorObserver(
       ScreenRotationAnimatorObserver* observer);
 
-  void OnLayerAnimationEnded();
-
-  void OnLayerAnimationAborted();
+  // When screen rotation animation is ended or aborted, calls |Rotate()| with
+  // the pending rotation request if the request queue is not empty. Otherwise
+  // notifies |screen_rotation_animator_observer_|.
+  void ProcessAnimationQueue();
 
  private:
   friend class ash::test::ScreenRotationAnimatorTestApi;
   struct ScreenRotationRequest;
+  class ScreenRotationAnimationMetricsReporter;
 
   // Set the screen orientation to |new_rotation| and animate the change. The
   // animation will rotate the initial orientation's layer towards the new
   // orientation through |rotation_degrees| while fading out, and the new
   // orientation's layer will be rotated in to the |new_orientation| through
   // |rotation_degrees| arc.
   void AnimateRotation(std::unique_ptr<ScreenRotationRequest> rotation_request);
 
-  // When screen rotation animation is ended or aborted, if the request queue is
-  // not empty, it will call |Rotate()| with the pending rotation request.
-  // Otherwise it will notify |screen_rotation_animator_observer_|.
-  void ProcessAnimationQueue();
-
   void set_disable_animation_timers_for_test(bool disable_timers);
 
   void StopAnimating();
 
   // The id of the display to rotate.
   int64_t display_id_;
   bool is_rotating_;
+  std::unique_ptr<ScreenRotationAnimationMetricsReporter> metrics_reporter_;

[oshima, 2017/03/24 22:46:00]

nit: you can just use ui::AnimationMetricsReporter, then hide the impl in .cc

[wutao, 2017/03/24 23:50:55]

Good suggestion. Done and Thanks.

   // Only set in unittest to disable animation timers.
   bool disable_animation_timers_for_test_;
   base::ObserverList<ScreenRotationAnimatorObserver>
       screen_rotation_animator_observers_;
   std::unique_ptr<ui::LayerTreeOwner> old_layer_tree_owner_;
   std::unique_ptr<ScreenRotationRequest> last_pending_request_;
   base::WeakPtrFactory<ScreenRotationAnimator> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenRotationAnimator);
 };
 
 }  // namespace ash
 
 #endif  // ASH_ROTATOR_SCREEN_ROTATION_ANIMATOR_H_