Remove #pragma once from ash

ash/system/tray/system_tray_delegate.h

 // 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.
 
 #ifndef ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_
-#pragma once
 
 #include <string>
 #include <vector>
 
 #include "ash/ash_export.h"
 #include "ash/system/power/power_supply_status.h"
 #include "ash/system/user/login_status.h"
 #include "base/file_path.h"
 #include "base/i18n/time_formatting.h"
 #include "base/string16.h"
@@ skipping 259 matching lines @@
   // Opens the cellular network specific URL.
   virtual void ShowCellularURL(const std::string& url) = 0;
 
   // Shows UI for changing proxy settings.
   virtual void ChangeProxySettings() = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_