Add device policy to disallow shutdown - ash UI modifications

ash/system/tray/default_system_tray_delegate.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_SYSTEM_TRAY_DEFAULT_SYSTEM_TRAY_DELEGATE_H_
 #define ASH_SYSTEM_TRAY_DEFAULT_SYSTEM_TRAY_DELEGATE_H_
 
 #include "ash/ash_export.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "base/compiler_specific.h"
@@ skipping 65 matching lines @@
   bool GetSessionLengthLimit(base::TimeDelta* session_length_limit) override;
   int GetSystemTrayMenuWidth() override;
   void ActiveUserWasChanged() override;
   bool IsSearchKeyMappedToCapsLock() override;
   tray::UserAccountsDelegate* GetUserAccountsDelegate(
       const std::string& user_id) override;
   void AddCustodianInfoTrayObserver(
       CustodianInfoTrayObserver* observer) override;
   void RemoveCustodianInfoTrayObserver(
       CustodianInfoTrayObserver* observer) override;
+  void AddShutdownPolicyObserver(ShutdownPolicyObserver* observer) override;
+  void RemoveShutdownPolicyObserver(ShutdownPolicyObserver* observer) override;
+  void ShouldRebootOnShutdown(
+      const RebootOnShutdownCallback& callback) override;
 
  private:
   bool bluetooth_enabled_;
   scoped_ptr<VolumeControlDelegate> volume_control_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(DefaultSystemTrayDelegate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_DEFAULT_SYSTEM_TRAY_DELEGATE_H_