I am trying to set up a web proxy for chromium on my 12.10 lubuntu box. In firefox I simply add the address of the autoconfigure script http://ipaddress/autoconfig in the "Automatic proxy configuration" box in preferences->network->settings and it works perfectly.

In chromium I have tried various possible solutions, all of which have failed so far. What is the right way to do this?

The solution given below works but uses the same proxy for all web pages and requires you to use a command line argument when you run chromium.

Is there a way to do the equivalent of what firefox does? That is load
the autoconfigure script (a javascript file) telling chromium which
URLs should use the proxy (see e.g.
http://en.wikipedia.org/wiki/Proxy_auto-config )?

That is I would like chromium to only use the proxy for selected pages. I would also like to be able easily to turn the proxy on and off.