chromeos: Simplify ShutdownPolicyHandler

ash/common/system/tray/system_tray_delegate.cc

 // Copyright (c) 2012 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.
 
 #include "ash/common/system/tray/system_tray_delegate.h"
 
 #include "ash/common/system/tray/ime_info.h"
 #include "ash/common/system/tray/system_tray_item.h"
 
 namespace ash {
@@ skipping 142 matching lines @@
 
 void SystemTrayDelegate::RemoveCustodianInfoTrayObserver(
     CustodianInfoTrayObserver* observer) {}
 
 void SystemTrayDelegate::AddShutdownPolicyObserver(
     ShutdownPolicyObserver* observer) {}
 
 void SystemTrayDelegate::RemoveShutdownPolicyObserver(
     ShutdownPolicyObserver* observer) {}
 
-void SystemTrayDelegate::ShouldRebootOnShutdown(
-    const RebootOnShutdownCallback& callback) {}
+void SystemTrayDelegate::CheckIfRebootOnShutdown() {}
 
 VPNDelegate* SystemTrayDelegate::GetVPNDelegate() const {
   return nullptr;
 }
 
 std::unique_ptr<SystemTrayItem> SystemTrayDelegate::CreateRotationLockTrayItem(
     SystemTray* tray) {
   return nullptr;
 }
 
 }  // namespace ash