bool execCommand(String commandId, [ bool showUI, String value ])

Source 

bool execCommand(String commandId, [bool showUI, String value]) {
  if (value != null) {
    return _blink.BlinkDocument.instance.execCommand_Callback_3_(this, commandId, showUI, value);
  }
  if (showUI != null) {
    return _blink.BlinkDocument.instance.execCommand_Callback_2_(this, commandId, showUI);
  }
  return _blink.BlinkDocument.instance.execCommand_Callback_1_(this, commandId);
}