Let SyncManagerFactory create different types of sync managers according to

sync/internal_api/public/sync_manager_factory.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 SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_FACTORY_H_
 #define SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_FACTORY_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "sync/base/sync_export.h"
 
 namespace syncer {
 
 class SyncManager;
 
 // Helper class to allow dependency injection of the SyncManager.
 class SYNC_EXPORT SyncManagerFactory {
  public:
-  SyncManagerFactory();
+  enum MANAGER_TYPE {
+    NORMAL,     // Normal sync manager
+    BACKUP,     // Backup sync manager
+    ROLLBACK,   // Rollback sync manager
+  };
+
+  SyncManagerFactory(MANAGER_TYPE type);
   virtual ~SyncManagerFactory();
 
   virtual scoped_ptr<SyncManager> CreateSyncManager(std::string name);
 
  private:
+  MANAGER_TYPE type_;
   DISALLOW_COPY_AND_ASSIGN(SyncManagerFactory);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_FACTORY_H_