Cleanup coding style

extensions/common/extension_set.h

 // Copyright 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_EXTENSION_SET_H_
 #define EXTENSIONS_COMMON_EXTENSION_SET_H_
 
 #include <iterator>
 #include <map>
 #include <string>
+#include <utility>
 
 #include "base/callback_forward.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "extensions/common/extension.h"
 #include "url/gurl.h"
 
 namespace extensions {
 
 // The one true extension container. Extensions are identified by their id.
@@ skipping 123 matching lines @@
   // discarding the set (e.g., on shutdown) and we do not want to track that as
   // a real modification.
   ModificationCallback modification_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionSet);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_EXTENSION_SET_H_