Add an action for server to send down rollback command.

sync/protocol/sync_protocol_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_PROTOCOL_SYNC_PROTOCOL_ERROR_H_
 #define SYNC_PROTOCOL_SYNC_PROTOCOL_ERROR_H_
 
 #include <string>
 
 #include "base/values.h"
 #include "sync/base/sync_export.h"
@@ skipping 44 matching lines @@
 
   // Set the bit on the account to enable sync.
   ENABLE_SYNC_ON_ACCOUNT,
 
   // Stop sync and restart sync.
   STOP_AND_RESTART_SYNC,
 
   // Wipe this client of any sync data.
   DISABLE_SYNC_ON_CLIENT,
 
+  // Disable sync and roll back local model to pre-sync state.
+  DISABLE_SYNC_AND_ROLLBACK,
+
   // Account is disabled by admin. Stop sync, clear prefs and show message on
   // settings page that account is disabled.
   STOP_SYNC_FOR_DISABLED_ACCOUNT,
 
   // The default. No action.
   UNKNOWN_ACTION
 };
 
 struct SYNC_EXPORT SyncProtocolError {
   SyncProtocolErrorType error_type;
   std::string error_description;
   std::string url;
   ClientAction action;
   ModelTypeSet error_data_types;
   SyncProtocolError();
   ~SyncProtocolError();
   base::DictionaryValue* ToValue() const;
 };
 
 SYNC_EXPORT const char* GetSyncErrorTypeString(SyncProtocolErrorType type);
 SYNC_EXPORT const char* GetClientActionString(ClientAction action);
 }  // namespace syncer
 #endif  // SYNC_PROTOCOL_SYNC_PROTOCOL_ERROR_H_