Watir-webdriver changes the proxy while keeping the browser open


I am using the Watir-Webdriver library in Ruby to check some pages. I know I can connect through a proxy using

profile = Selenium::WebDriver::Firefox::Profile.new#create a new profile
profile.proxy = Selenium::WebDriver::Proxy.new(#create proxy data for in the profile
  :http => proxyadress,
  :ftp => nil,
  :ssl => nil,
  :no_proxy => nil
browser = Watir::Browser.new :firefox, :profile => profile#create a browser window with this profile
browser.goto "http://www.example.com"

However, when wanting to connect to the same page multiple times using different proxies, I have to create a new browser for every proxy. Loading(and unloading) the browser takes quite some time.

So, my question: Is there any way to change, using webdriver in ruby, the proxy adress Firefox uses to connect through while keeping the browser open?

If you want to test whether a page is blocked when accessed through a proxy server, you can do that through a headless library. I recently had success using mechanize. You can probably use net/http as well.

I am still not sure why you need to change the proxy server for a current session.

require 'Mechanize'
session = Mechanize.new
session.set_proxy(host, port, user, pass)
session.user_agent='Mac Safari'
session.agent.robots = true #observe of robots.txt rules
response = session.get(url)
puts response.code

You need to supply the proxy host/port/user/pass (user/pass are optional), and the url. If you get an exception, then the response.code is probably not friendly.