[Sync] Refactoring polling to be reliable.

sync/internal_api/sync_rollback_manager.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 SYNC_INTERNAL_API_SYNC_ROLLBACK_MANAGER_H_
 #define SYNC_INTERNAL_API_SYNC_ROLLBACK_MANAGER_H_
 
 #include <string>
 #include <vector>
 
 #include "sync/internal_api/sync_rollback_manager_base.h"
 
 class GURL;
 
 namespace syncer {
 
 // SyncRollbackManager restores user's data to pre-sync state using backup
 // DB created by SyncBackupManager.
 class SYNC_EXPORT_PRIVATE SyncRollbackManager : public SyncRollbackManagerBase {
  public:
   SyncRollbackManager();
   ~SyncRollbackManager() override;
 
   // SyncManager implementation.
   void Init(InitArgs* args) override;
-  void StartSyncingNormally(const ModelSafeRoutingInfo& routing_info) override;
+  void StartSyncingNormally(const ModelSafeRoutingInfo& routing_info,
+                            base::Time last_poll_time) override;
 
  private:
   // Deletes specified entries in local model.
   SyncerError DeleteOnWorkerThread(ModelType type, std::vector<int64> handles);
 
   void NotifyRollbackDone();
 
   std::map<ModelSafeGroup, scoped_refptr<ModelSafeWorker> > workers_;
 
   SyncManager::ChangeDelegate* change_delegate_;
 
   // Types that can be rolled back.
   ModelTypeSet rollback_ready_types_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncRollbackManager);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_SYNC_ROLLBACK_MANAGER_H_