void queryUsageAndQuota(int storageType, [ StorageUsageCallback usageCallback, StorageErrorCallback errorCallback ])

Source 

void queryUsageAndQuota(int storageType,
    [StorageUsageCallback usageCallback,
    StorageErrorCallback errorCallback]) {
  if (errorCallback != null) {
    _blink.BlinkDeprecatedStorageInfo.instance.queryUsageAndQuota_Callback_3_(
        this, storageType, usageCallback, errorCallback);
    return;
  }
  if (usageCallback != null) {
    _blink.BlinkDeprecatedStorageInfo.instance
        .queryUsageAndQuota_Callback_2_(this, storageType, usageCallback);
    return;
  }
  _blink.BlinkDeprecatedStorageInfo.instance
      .queryUsageAndQuota_Callback_1_(this, storageType);
  return;
}