Cleanup: fix Namespace comments in /extension/commons

extensions/common/install_warning.h

 // Copyright (c) 2013 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 EXTENSIONS_COMMON_INSTALL_WARNING_H_
 #define EXTENSIONS_COMMON_INSTALL_WARNING_H_
 
 #include <ostream>
 #include <string>
 
@@ skipping 25 matching lines @@
   // "permissions").
   std::string key;
   // Optional - for specifying the incorrect portion of a key in the manifest
   // (e.g., an unrecognized permission "foo" in "permissions").
   std::string specific;
 };
 
 // Let gtest print InstallWarnings.
 void PrintTo(const InstallWarning&, ::std::ostream* os);
 
-}  // namespace
+}  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_INSTALL_WARNING_H_