components: Cleanup class/struct fwd declarations

components/content_settings/core/browser/content_settings_pref_provider.h

 // Copyright (c) 2012 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 COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_CONTENT_SETTINGS_PREF_PROVIDER_H_
 #define COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_CONTENT_SETTINGS_PREF_PROVIDER_H_
 
 // A content settings provider that takes its settings out of the pref service.
 
 #include <map>
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "components/content_settings/core/browser/content_settings_observable_provider.h"
 #include "components/content_settings/core/browser/content_settings_utils.h"
 #include "components/prefs/pref_change_registrar.h"
 
 class PrefService;
 
 namespace base {
 class Clock;
-class DictionaryValue;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 namespace content_settings {
 
 class ContentSettingsPref;
 
@@ skipping 63 matching lines @@
       content_settings_prefs_;
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefProvider);
 };
 
 }  // namespace content_settings
 
 #endif  // COMPONENTS_CONTENT_SETTINGS_CORE_BROWSER_CONTENT_SETTINGS_PREF_PROVIDER_H_