ios: Cleanup class/struct forward declarations

ios/chrome/browser/notification_promo.h

 // Copyright (c) 2016 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 IOS_CHROME_BROWSER_NOTIFICATION_PROMO_H_
 #define IOS_CHROME_BROWSER_NOTIFICATION_PROMO_H_
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 
 class PrefRegistrySimple;
 class PrefService;
 
 namespace base {
 class DictionaryValue;
-class ListValue;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 namespace ios {
 
 // Class that parses and manages promotion data from either a finch trial, json,
 // or prefs.
@@ skipping 93 matching lines @@
 
   int views_;
   bool closed_;
 
   DISALLOW_COPY_AND_ASSIGN(NotificationPromo);
 };
 
 }  // namespace ios
 
 #endif  // IOS_CHROME_BROWSER_NOTIFICATION_PROMO_H_