c/b/supervised_user: Use range-based for where appropriate.

chrome/browser/supervised_user/supervised_user_pref_store.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 CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_PREF_STORE_H_
 #define CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_PREF_STORE_H_
 
+#include <string>
+
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/prefs/pref_store.h"
 #include "chrome/browser/supervised_user/supervised_users.h"
 
 namespace base {
 class DictionaryValue;
 class Value;
 }
 
@@ skipping 21 matching lines @@
   void OnNewSettingsAvailable(const base::DictionaryValue* settings);
 
   scoped_ptr<PrefValueMap> prefs_;
 
   ObserverList<PrefStore::Observer, true> observers_;
 
   base::WeakPtrFactory<SupervisedUserPrefStore> weak_ptr_factory_;
 };
 
 #endif  // CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_PREF_STORE_H_