void requestQuota(int newQuotaInBytes, [StorageQuotaCallback quotaCallback(int grantedQuotaInBytes), StorageErrorCallback errorCallback(DomError error)])

Source 

void requestQuota(int newQuotaInBytes, [StorageQuotaCallback quotaCallback, StorageErrorCallback errorCallback]) {
  if (errorCallback != null) {
    _blink.BlinkDeprecatedStorageQuota.instance.requestQuota_Callback_3_(this, newQuotaInBytes, quotaCallback, errorCallback);
    return;
  }
  if (quotaCallback != null) {
    _blink.BlinkDeprecatedStorageQuota.instance.requestQuota_Callback_2_(this, newQuotaInBytes, quotaCallback);
    return;
  }
  _blink.BlinkDeprecatedStorageQuota.instance.requestQuota_Callback_1_(this, newQuotaInBytes);
  return;
}