chrome: Cleanup class/struct forward declarations

chrome/browser/chromeos/login/session/user_session_manager.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_CHROMEOS_LOGIN_SESSION_USER_SESSION_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SESSION_USER_SESSION_MANAGER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 12 matching lines @@
 #include "chromeos/login/auth/authenticator.h"
 #include "chromeos/login/auth/user_context.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_manager.h"
 #include "net/base/network_change_notifier.h"
 #include "ui/base/ime/chromeos/input_method_manager.h"
 
 class AccountId;
 class GURL;
 class PrefRegistrySimple;
-class PrefService;
 class Profile;
 class TokenHandleFetcher;
 
 namespace net {
 class URLRequestContextGetter;
 }
 
 namespace user_manager {
 class User;
 }  // namespace user_manager
@@ skipping 458 matching lines @@
       hats_notification_controller_;
 
   base::WeakPtrFactory<UserSessionManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UserSessionManager);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SESSION_USER_SESSION_MANAGER_H_