components: Cleanup class/struct fwd declarations

components/sync/engine_impl/directory_update_handler.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 COMPONENTS_SYNC_ENGINE_IMPL_DIRECTORY_UPDATE_HANDLER_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_DIRECTORY_UPDATE_HANDLER_H_
 
 #include <map>
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "components/sync/base/model_type.h"
 #include "components/sync/base/syncer_error.h"
 #include "components/sync/engine_impl/process_updates_util.h"
 #include "components/sync/engine_impl/update_handler.h"
 
 namespace sync_pb {
 class DataTypeProgressMarker;
 class GarbageCollectionDirective;
-class GetUpdatesResponse;
 }
 
 namespace syncer {
 
 class DataTypeDebugInfoEmitter;
 class ModelSafeWorker;
 class StatusController;
 
 namespace syncable {
 class Directory;
@@ skipping 69 matching lines @@
   DataTypeDebugInfoEmitter* debug_info_emitter_;
 
   std::unique_ptr<sync_pb::GarbageCollectionDirective> cached_gc_directive_;
 
   DISALLOW_COPY_AND_ASSIGN(DirectoryUpdateHandler);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_DIRECTORY_UPDATE_HANDLER_H_