void readAsText(Blob blob, [String label])

Source 

void readAsText(Blob blob, [String label]) {
  if (label != null) {
    _blink.BlinkFileReader.instance.readAsText_Callback_2_(this, blob, label);
    return;
  }
  _blink.BlinkFileReader.instance.readAsText_Callback_1_(this, blob);
  return;
}