Remove #pragma once from chrome/browser/extensions

chrome/browser/extensions/external_registry_extension_loader_win.h

 // Copyright (c) 2011 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 CHROME_BROWSER_EXTENSIONS_EXTERNAL_REGISTRY_EXTENSION_LOADER_WIN_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTERNAL_REGISTRY_EXTENSION_LOADER_WIN_H_
-#pragma once
 
 #include "base/compiler_specific.h"
 #include "chrome/browser/extensions/external_extension_loader.h"
 
 class ExternalRegistryExtensionLoader : public ExternalExtensionLoader {
  public:
   ExternalRegistryExtensionLoader() {}
 
  protected:
   virtual void StartLoading() OVERRIDE;
 
  private:
   friend class base::RefCountedThreadSafe<ExternalExtensionLoader>;
 
   virtual ~ExternalRegistryExtensionLoader() {}
 
   void LoadOnFileThread();
 
   DISALLOW_COPY_AND_ASSIGN(ExternalRegistryExtensionLoader);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_REGISTRY_EXTENSION_LOADER_WIN_H_