chrome: Cleanup class/struct forward declarations

chrome/browser/content_settings/content_settings_supervised_provider.h

 // Copyright (c) 2015 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_CONTENT_SETTINGS_CONTENT_SETTINGS_SUPERVISED_PROVIDER_H_
 #define CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_SUPERVISED_PROVIDER_H_
 
 // A content setting provider that is set by the custodian of a supervised user.
 
 #include "base/callback_list.h"
 #include "base/macros.h"
 #include "base/synchronization/lock.h"
 #include "components/content_settings/core/browser/content_settings_binary_value_map.h"
 #include "components/content_settings/core/browser/content_settings_observable_provider.h"
 
-class PrefService;
 class SupervisedUserSettingsService;
 
 namespace content_settings {
 
 // SupervisedProvider that provides content-settings managed by the custodian
 // of a supervised user.
 class SupervisedProvider : public ObservableProvider {
  public:
   explicit SupervisedProvider(
       SupervisedUserSettingsService* supervised_user_settings_service);
@@ skipping 28 matching lines @@
   std::unique_ptr<
       base::CallbackList<void(const base::DictionaryValue*)>::Subscription>
       user_settings_subscription_;
 
   DISALLOW_COPY_AND_ASSIGN(SupervisedProvider);
 };
 
 }  // namespace content_settings
 
 #endif  // CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_SUPERVISED_PROVIDER_H_