chrome: Cleanup class/struct forward declarations

chrome/browser/ui/prefs/prefs_tab_helper.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 CHROME_BROWSER_UI_PREFS_PREFS_TAB_HELPER_H_
 #define CHROME_BROWSER_UI_PREFS_PREFS_TAB_HELPER_H_
 
 #include "base/callback_list.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/ui/zoom/chrome_zoom_level_prefs.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_contents_user_data.h"
 
-class OverlayUserPrefStore;
-class PrefService;
 class Profile;
 
 namespace content {
 class WebContents;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
@@ skipping 34 matching lines @@
   std::unique_ptr<base::CallbackList<void(void)>::Subscription>
       style_sheet_subscription_;
   std::unique_ptr<ChromeZoomLevelPrefs::DefaultZoomLevelSubscription>
       default_zoom_level_subscription_;
   base::WeakPtrFactory<PrefsTabHelper> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefsTabHelper);
 };
 
 #endif  // CHROME_BROWSER_UI_PREFS_PREFS_TAB_HELPER_H_