WebDriver Proxy setting does not work

[loyalchow]

Meta -

OS: Mac OS X 10.11.5
Selenium Version: 2.53.2

Expected Behavior -

Expect selenium-webdriver to connect to a remote Selenium server through a proxy when using usingWebDriverProxy.

Actual Behavior -

selenium-webdriver does not proxy requests correctly to remote Selenium server, even when usingWebDriverProxy option is set correctly. Instead, it sends webdriver requests directly to the proxy server.

Steps to reproduce -

1. On Mac, install and run SquidMan proxy server on port 8080 (default settings)
2. Run the code below using NodeJS, which attempts to connect to a remote Selenium server.
3. When run, will output an error. Should instead get "successful connection using proxy" message.

var webdriver = require('selenium-webdriver');
new webdriver.Builder()
    .forBrowser('chrome')
    .usingWebDriverProxy('http://localhost:8080')
    .usingServer('http://ondemand.saucelabs.com/wd/hub')
    .buildAsync()
    .then(function(driver) {
        driver.quit();
    })
    .catch(function(ex) {
        var err = ex.stack.toString();
        if (err.indexOf('Sauce Labs Authentication Error') > -1) {
            return console.log('Successful connection using proxy!')
        }
        console.error(err);
    });