Node.js 为Firefox设置自定义用户代理-selenium standalone/WebDriverSangular

我正在将selenium standalone与一起使用，并尝试设置自定义用户代理

var selenium = require('selenium-standalone');
var webdriverjsAngular = require('webdriverjs-angular');
var FirefoxProfile = require('firefox-profile');
var myProfile = new FirefoxProfile();
myProfile.setPreference("general.useragent.override", "custom-user-agent");


var webDriverOptions = {
    desiredCapabilities: {
        browserName: 'firefox',
        firefox_profile: myProfile
    }
};
var seleniumOptions = {
    drivers: {
        chrome: {
            version: '2.9',
            arch: process.arch,
            baseURL: 'https://chromedriver.storage.googleapis.com'
        },
    },
};

selenium.start(seleniumOptions, function(err, child) {
    webdriverjsAngular.remote(webDriverOptions)
     .....
}

代码正在运行，除了未使用

firefox配置文件的设置之外，firefox仍在使用此用户代理：
Mozilla/5.0（X11；Ubuntu；Linux x86_64；rv:44.0）Gecko/20100101 firefox/44.0

如何设置自定义用户代理？
我缺少最后一部分：

var myProfile = new FirefoxProfile();
myProfile.setPreference("general.useragent.override", "custom-user-agent");    

myProfile.encoded(function (encodedProfile) {
    // output the generated encoded profile as stdout
    // NOTE: if an error occurs with the encodedProfile then the default Firefox settings will be used in your tests    
  var webDriverOptions = {
      desiredCapabilities: {
          browserName: 'firefox',
          firefox_profile: encodedProfile
      }
  };
});