Move Extension into extensions namespace

chrome/browser/extensions/extension_webkit_preferences.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_EXTENSION_WEBKIT_PREFERENCES_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_WEBKIT_PREFERENCES_H_
 
 #include "chrome/common/chrome_view_type.h"
 
+namespace extensions {
 class Extension;
+}
 
 namespace webkit_glue {
 struct WebPreferences;
 }
 
 namespace extension_webkit_preferences {
 
-void SetPreferences(const Extension* extension,
+void SetPreferences(const extensions::Extension* extension,
                     content::ViewType render_view_type,
                     webkit_glue::WebPreferences* webkit_prefs);
 
 }  // namespace extension_webkit_preferences
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_WEBKIT_PREFERENCES_H_