components: Cleanup class/struct fwd declarations

components/sync/engine_impl/cycle/sync_cycle.h

 // Copyright 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_SYNC_ENGINE_IMPL_CYCLE_SYNC_CYCLE_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_CYCLE_SYNC_CYCLE_H_
 
 #include <map>
 #include <memory>
 #include <set>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "components/sync/base/model_type.h"
 #include "components/sync/engine/cycle/sync_cycle_snapshot.h"
 #include "components/sync/engine/model_safe_worker.h"
 #include "components/sync/engine_impl/cycle/status_controller.h"
 #include "components/sync/engine_impl/cycle/sync_cycle_context.h"
 #include "components/sync/engine_impl/sync_cycle_event.h"
 #include "components/sync/protocol/sync_protocol_error.h"
 
 namespace syncer {
 
-class ModelSafeWorker;
-class NudgeTracker;
 class ProtocolEvent;
 
 // A class representing an attempt to synchronize the local syncable data
 // store with a sync server. A SyncCycle instance is passed as a stateful
 // bundle throughout the sync cycle.  The SyncCycle is not reused across
 // sync cycles; each cycle starts with a new one.
 class SyncCycle {
  public:
   // The Delegate services events that occur during the cycle requiring an
   // explicit (and cycle-global) action, as opposed to events that are simply
@@ skipping 91 matching lines @@
 
   // Our controller for various status and error counters.
   std::unique_ptr<StatusController> status_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncCycle);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_CYCLE_SYNC_CYCLE_H_