Add an action for server to send down rollback command.

sync/internal_api/public/util/syncer_error.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_UTIL_SYNCER_ERROR_H_
 #define SYNC_INTERNAL_API_PUBLIC_UTIL_SYNCER_ERROR_H_
 
 #include "sync/base/sync_export.h"
 
 namespace syncer {
@@ skipping 12 matching lines @@
   SERVER_RETURN_INVALID_CREDENTIAL,
   SERVER_RETURN_UNKNOWN_ERROR,
   SERVER_RETURN_THROTTLED,
   SERVER_RETURN_TRANSIENT_ERROR,
   SERVER_RETURN_MIGRATION_DONE,
   SERVER_RETURN_CLEAR_PENDING,
   SERVER_RETURN_NOT_MY_BIRTHDAY,
   SERVER_RETURN_CONFLICT,
   SERVER_RESPONSE_VALIDATION_FAILED,
   SERVER_RETURN_DISABLED_BY_ADMIN,
+  SERVER_RETURN_USER_ROLLBACK,
 
   // A datatype decided the sync cycle needed to be performed again.
   DATATYPE_TRIGGERED_RETRY,
 
   SERVER_MORE_TO_DOWNLOAD,
 
   SYNCER_OK
 };
 
 SYNC_EXPORT const char* GetSyncerErrorString(SyncerError);
 
 // Helper to check that |error| is set to something (not UNSET) and is not
 // SYNCER_OK.
 bool SyncerErrorIsError(SyncerError error);
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_UTIL_SYNCER_ERROR_H_