int requestIdleCallback(IdleRequestCallback callback, [ Map options ])

Source 

int requestIdleCallback(IdleRequestCallback callback, [Map options]) {
  if (options != null) {
    return _blink.BlinkWindow.instance.requestIdleCallback_Callback_2_(
        this, callback, convertDartToNative_Dictionary(options));
  }
  return _blink.BlinkWindow.instance
      .requestIdleCallback_Callback_1_(this, callback);
}