Move c/r/extensions/* into extensions namespace

chrome/renderer/extensions/extension_groups.h

 // Copyright (c) 2009 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_RENDERER_EXTENSIONS_EXTENSION_GROUPS_H_
 #define CHROME_RENDERER_EXTENSIONS_EXTENSION_GROUPS_H_
 
+namespace extensions {
+
 // A set of extension groups for use with WebKit::registerExtension and
 // WebFrame::ExecuteScriptInNewWorld to control which extensions get loaded
 // into which contexts.
 enum ExtensionGroups {
   // Use this to mark extensions to be loaded into content scripts only.
   EXTENSION_GROUP_CONTENT_SCRIPTS = 1,
 };
 
+}  // namespace extensions
 
 #endif  // CHROME_RENDERER_EXTENSIONS_EXTENSION_GROUPS_H_