chromeos: Move device shutdown handling out of chrome into ash

ash/common/system/chromeos/shutdown_policy_observer.h

-// Copyright 2014 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_COMMON_SYSTEM_CHROMEOS_SHUTDOWN_POLICY_OBSERVER_H_
-#define ASH_COMMON_SYSTEM_CHROMEOS_SHUTDOWN_POLICY_OBSERVER_H_
-
-#include "ash/ash_export.h"
-
-namespace ash {
-
-// Registered with SystemTrayDelegate to observe the |kRebootOnShutdown| policy.
-class ASH_EXPORT ShutdownPolicyObserver {
- public:
-  // Called when the value of the |kRebootOnShutdown| policy is changed.
-  virtual void OnShutdownPolicyChanged(bool reboot_on_shutdown) = 0;
-
- protected:
-  virtual ~ShutdownPolicyObserver() {}
-};
-
-}  // namespace ash
-
-#endif  // ASH_COMMON_SYSTEM_CHROMEOS_SHUTDOWN_POLICY_OBSERVER_H_