chromeos: Move device shutdown handling out of chrome into ash

ash/public/interfaces/shutdown.mojom

 // Copyright 2016 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.
 
 module ash.mojom;
 
-// Interface implemented by service:content_browser to activate shutdown.
-//
-// TODO(erg): Eventually, when CrosSettings is moved out of chrome into its
-// own process, this client should go away. The code which actually calls
-// shutdown should be moved into ash/, and ash should subscribe to changes
-// in CrosSettings. crbug.com/628792
-interface ShutdownClient {
-  // Requests that the system shuts down.
-  RequestShutdown();
+// Interface implemented by ash and used by chrome to provide shutdown policy
+// information. Exists because device policy is owned by chrome, not ash.
+interface ShutdownController {
+  // Sets a boolean pref that indicates whether the device automatically reboots
+  // when the user initiates a shutdown via an UI element. Used in enterprise
+  // environments for devices that should not be shut down.
+  SetRebootOnShutdown(bool reboot_on_shutdown);
 };