components: Cleanup class/struct fwd declarations

components/sync/driver/non_ui_data_type_controller.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_DRIVER_NON_UI_DATA_TYPE_CONTROLLER_H_
 #define COMPONENTS_SYNC_DRIVER_NON_UI_DATA_TYPE_CONTROLLER_H_
 
 #include <memory>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "components/sync/driver/directory_data_type_controller.h"
 #include "components/sync/driver/shared_change_processor.h"
 
 namespace syncer {
 
 class SyncClient;
-class SyncableService;
 struct UserShare;
 
 class NonUIDataTypeController : public DirectoryDataTypeController {
  public:
   // |dump_stack| is called when an unrecoverable error occurs.
   NonUIDataTypeController(ModelType type,
                           const base::Closure& dump_stack,
                           SyncClient* sync_client);
   ~NonUIDataTypeController() override;
 
@@ skipping 95 matching lines @@
   // released on the UI thread in Stop()/StartDoneImpl(), but the
   // backend thread may still have references to it (which is okay,
   // since we call Disconnect() before releasing the UI thread
   // reference).
   scoped_refptr<SharedChangeProcessor> shared_change_processor_;
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_DRIVER_NON_UI_DATA_TYPE_CONTROLLER_H_