Move Extension into extensions namespace

chrome/browser/extensions/unpacked_installer.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 CHROME_BROWSER_EXTENSIONS_UNPACKED_INSTALLER_H_
 #define CHROME_BROWSER_EXTENSIONS_UNPACKED_INSTALLER_H_
 #pragma once
 
 #include <string>
 
 #include "base/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 
-class Extension;
 class ExtensionService;
 
 namespace extensions {
 
+class Extension;
+
 // Installs and loads an unpacked extension.
 // TODO(erikkay): It might be useful to be able to load a packed extension
 // (presumably into memory) without installing it.
 class UnpackedInstaller
     : public base::RefCountedThreadSafe<UnpackedInstaller> {
  public:
   static scoped_refptr<UnpackedInstaller> Create(
       ExtensionService* extension_service);
 
   // Loads the extension from the directory |extension_path|, which is
@@ skipping 46 matching lines @@
   // If true and the extension contains plugins, we prompt the user before
   // loading.
   bool prompt_for_plugins_;
 
   DISALLOW_COPY_AND_ASSIGN(UnpackedInstaller);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_UNPACKED_INSTALLER_H_