code: function SeleniumServer(jar, options) {
    if (options.port < 0)
      throw Error('Port must be >= 0: ' + options.port);
  
    var port = options.port || portprober.findFreePort();
    var args = promise.when(options.jvmArgs || [], function(jvmArgs) {
      return promise.when(options.args || [], function(args) {
        return promise.when(port, function(port) {
          return jvmArgs.concat(['-jar', jar, '-port', port]).concat(args);
        });
      });
    });
  
    DriverService.call(this, 'java', {
      port: port,
      args: args,
      path: '/wd/hub',
      env: options.env,
      stdio: options.stdio
    });
  }
docs: Manages the life and death of the Selenium standalone server. The server
  may be obtained from http://selenium-release.storage.googleapis.com/index.html.
  @param {string} jar Path to the Selenium server jar.
  @param {!SeleniumServer.Options} options Configuration options for the
  server.
  @throws {Error} If an invalid port is specified.
  @constructor
  @extends {DriverService}