mash: Migrate ShelfLockingManager to ash/common.

ash/wm/lock_state_observer.h

-// Copyright 2013 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_WM_LOCK_STATE_OBSERVER_H_
-#define ASH_WM_LOCK_STATE_OBSERVER_H_
-
-#include "ash/ash_export.h"
-
-namespace ash {
-
-// Interface for classes that want to be notified by LockStateController when
-// session-related events occur.
-class ASH_EXPORT LockStateObserver {
- public:
-  enum EventType {
-    EVENT_PRELOCK_ANIMATION_STARTED,
-    EVENT_LOCK_ANIMATION_STARTED,
-    EVENT_LOCK_ANIMATION_FINISHED,
-  };
-
-  virtual void OnLockStateEvent(EventType event) = 0;
-  virtual ~LockStateObserver() {}
-};
-
-}  // namespace ash
-
-#endif  // ASH_WM_LOCK_STATE_OBSERVER_H_