Handles users rotating screen too early

ash/rotator/screen_rotation_animator_observer.h

Index: ash/rotator/screen_rotation_animator_observer.h
diff --git a/ash/rotator/screen_rotation_animator_observer.h b/ash/rotator/screen_rotation_animator_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..5689a96d5d8663e4b83de986fdbca8e91cf06b9c
--- /dev/null
+++ b/ash/rotator/screen_rotation_animator_observer.h
@@ -0,0 +1,28 @@
+// Copyright 2017 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_OBSERVER_H
+#define ASH_ROTATOR_SCREEN_ROTATION_ANIMATOR_OBSERVER_H
+
+#include "ash/ash_export.h"
+
+namespace ash {
+
+class ScreenRotationAnimator;
+
+class ASH_EXPORT ScreenRotationAnimatorObserver {
+ public:
+  ScreenRotationAnimatorObserver() {}
+
+  // This will be called when the animation is ended or aborted.
+  virtual void OnScreenRotationAnimationFinished(
+      ScreenRotationAnimator* animator) = 0;
+
+ protected:
+  virtual ~ScreenRotationAnimatorObserver() {}
+};
+
+}  // namespace ash
+
+#endif  // ASH_ROTATOR_SCREEN_ROTATION_ANIMATOR_OBSERVER_H