components: Cleanup class/struct fwd declarations

components/sync/engine_impl/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_UPDATE_HANDLER_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_UPDATE_HANDLER_H_
 
 #include <vector>
 
 #include "components/sync/base/syncer_error.h"
 
 namespace sync_pb {
 class DataTypeContext;
 class DataTypeProgressMarker;
 class SyncEntity;
 }
 
 typedef std::vector<const sync_pb::SyncEntity*> SyncEntityList;
 
 namespace syncer {
 
-class ModelSafeWorker;
 class StatusController;
 
 // This class represents an entity that can request, receive, and apply updates
 // from the sync server.
 class UpdateHandler {
  public:
   UpdateHandler();
   virtual ~UpdateHandler() = 0;
 
   // Returns true if initial sync was performed for this type.
@@ skipping 30 matching lines @@
   virtual void ApplyUpdates(StatusController* status) = 0;
 
   // Called at the end of a configure GetUpdates loop to perform any required
   // post-initial-download update application.
   virtual void PassiveApplyUpdates(StatusController* status) = 0;
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_UPDATE_HANDLER_H_