Clean-up coding style

extensions/common/features/permission_feature.h

 // Copyright 2014 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_FEATURES_PERMISSION_FEATURE_H_
 #define EXTENSIONS_COMMON_FEATURES_PERMISSION_FEATURE_H_
 
+#include <string>
+
 #include "extensions/common/features/simple_feature.h"
 
 namespace extensions {
 
 class PermissionFeature : public SimpleFeature {
  public:
   PermissionFeature();
   virtual ~PermissionFeature();
 
   virtual Feature::Availability IsAvailableToContext(
       const Extension* extension,
       Feature::Context context,
       const GURL& url,
       Feature::Platform platform) const OVERRIDE;
 
   virtual std::string Parse(const base::DictionaryValue* value) OVERRIDE;
 };
 
-}  // extensions
+}  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_FEATURES_PERMISSION_FEATURE_H_