Fix corner case if another rotation request comes before the copy request finishes.

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 94 matching lines @@
   // orientation's layer will be rotated in to the |new_orientation| through
   // |rotation_degrees| arc.
   void AnimateRotation(std::unique_ptr<ScreenRotationRequest> rotation_request);
 
   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_;
+
+  // For current slow rotation animation, there are two states |ROTATING| and
+  // |IDLE|. For the smooth rotation animation, we need to send copy request
+  // and get copy result before animating.
+  enum ScreenRotationState {
+    COPY_REQUESTED,
+    ROTATING,
+    IDLE,
+  };
+  ScreenRotationState screen_rotation_state_;
+
   std::unique_ptr<ui::AnimationMetricsReporter> metrics_reporter_;
   // 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_