chrome: Cleanup class/struct forward declarations

chrome/browser/invalidation/profile_invalidation_provider_factory.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_INVALIDATION_PROFILE_INVALIDATION_PROVIDER_FACTORY_H_
 #define CHROME_BROWSER_INVALIDATION_PROFILE_INVALIDATION_PROVIDER_FACTORY_H_
 
 #include "base/macros.h"
 #include "base/memory/singleton.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
 class Profile;
 
 namespace policy {
 class AffiliatedInvalidationServiceProviderImplTest;
 }
 
-namespace syncer {
-class Invalidator;
-}
-
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 namespace invalidation {
 
 class ProfileInvalidationProvider;
 
 // A BrowserContextKeyedServiceFactory to construct InvalidationServices wrapped
 // in ProfileInvalidationProviders. The implementation of InvalidationService
@@ skipping 30 matching lines @@
       user_prefs::PrefRegistrySyncable* registry) override;
 
   TestingFactoryFunction testing_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ProfileInvalidationProviderFactory);
 };
 
 }  // namespace invalidation
 
 #endif  // CHROME_BROWSER_INVALIDATION_PROFILE_INVALIDATION_PROVIDER_FACTORY_H_