Revert of Let SyncBackupManager keep backup data in memory until shutdown. Only persist

sync/internal_api/sync_backup_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_BACKUP_MANAGER_H_
 #define SYNC_INTERNAL_API_SYNC_BACKUP_MANAGER_H_
 
 #include <set>
 
 #include "sync/internal_api/sync_rollback_manager_base.h"
 #include "url/gurl.h"
 
 namespace syncer {
 
 // SyncBackupManager runs before user signs in to sync to back up user's data
 // before sync starts. The data that's backed up can be used to restore user's
 // settings to pre-sync state.
 class SYNC_EXPORT_PRIVATE SyncBackupManager : public SyncRollbackManagerBase {
  public:
   SyncBackupManager();
   virtual ~SyncBackupManager();
 
   // SyncManager implementation.
   virtual void Init(InitArgs* args) OVERRIDE;
   virtual void SaveChanges() OVERRIDE;
   virtual SyncStatus GetDetailedStatus() const OVERRIDE;
-  virtual void ShutdownOnSyncThread(ShutdownReason reason) OVERRIDE;
 
   // DirectoryChangeDelegate implementation.
   virtual ModelTypeSet HandleTransactionEndingChangeEvent(
       const syncable::ImmutableWriteTransactionInfo& write_transaction_info,
       syncable::BaseTransaction* trans) OVERRIDE;
 
   virtual void RegisterDirectoryTypeDebugInfoObserver(
       syncer::TypeDebugInfoObserver* observer) OVERRIDE;
   virtual void UnregisterDirectoryTypeDebugInfoObserver(
       syncer::TypeDebugInfoObserver* observer) OVERRIDE;
@@ skipping 19 matching lines @@
   bool in_normalization_;
 
   SyncStatus status_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackupManager);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_SYNC_BACKUP_MANAGER_H_