Let SyncManagerFactory create different types of sync managers according to

sync/internal_api/public/sync_manager_factory.h

Index: sync/internal_api/public/sync_manager_factory.h
diff --git a/sync/internal_api/public/sync_manager_factory.h b/sync/internal_api/public/sync_manager_factory.h
index 12fa52fdef81f7abe134ef84d5935010747c62ff..a121c8bf1f720b16c13d4dfd6572dbfca39c33bf 100644
--- a/sync/internal_api/public/sync_manager_factory.h
+++ b/sync/internal_api/public/sync_manager_factory.h
@@ -17,12 +17,19 @@ 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);
 };