code: function findSystemPortRange() {
    if (systemRange) {
      return systemRange;
    }
    var range = process.platform === 'win32' ?
        findWindowsPortRange() : findUnixPortRange();
    return systemRange = range.thenCatch(function() {
      return DEFAULT_IANA_RANGE;
    });
  }
docs: Computes the ephemeral port range for the current system. This is based on
  http://stackoverflow.com/a/924337.
  @return {webdriver.promise.Promise.<{min: number, max: number}>} A promise
  that will resolve to the ephemeral port range of the current system.