components: Cleanup class/struct fwd declarations

components/history/core/browser/typed_url_data_type_controller.h

 // Copyright (c) 2012 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_HISTORY_CORE_BROWSER_TYPED_URL_DATA_TYPE_CONTROLLER_H__
 #define COMPONENTS_HISTORY_CORE_BROWSER_TYPED_URL_DATA_TYPE_CONTROLLER_H__
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "components/prefs/pref_change_registrar.h"
 #include "components/sync/driver/non_ui_data_type_controller.h"
 #include "components/sync/driver/sync_api_component_factory.h"
 
-namespace history {
-class HistoryBackend;
-}
-
 namespace browser_sync {
 
-class ControlTask;
-
 // A class that manages the startup and shutdown of typed_url sync.
 class TypedUrlDataTypeController : public syncer::NonUIDataTypeController {
  public:
   // |dump_stack| is called when an unrecoverable error occurs.
   TypedUrlDataTypeController(const base::Closure& dump_stack,
                              syncer::SyncClient* sync_client,
                              const char* history_disabled_pref_name);
   ~TypedUrlDataTypeController() override;
 
   // NonUIDataTypeController implementation
@@ skipping 18 matching lines @@
   base::CancelableTaskTracker task_tracker_;
 
   syncer::SyncClient* const sync_client_;
 
   DISALLOW_COPY_AND_ASSIGN(TypedUrlDataTypeController);
 };
 
 }  // namespace browser_sync
 
 #endif  // COMPONENTS_HISTORY_CORE_BROWSER_TYPED_URL_DATA_TYPE_CONTROLLER_H__