Change user-agent depending on proxy

[GoogleCodeExporter]

It would be incredibly useful to specify a custom user-agent string for 
specific proxies.

Ideally you could enable or disable this per-proxy so certain proxies could use 
the Google Chrome default user-agent string but for other proxies you could 
specify your own.

Currently Chrome supports changing the user-agent via the command-line but I'm 
not sure what other APIs are available.

Original issue reported on code.google.com by jkli...@gmail.com on 7 Jul 2011 at 7:07

[GoogleCodeExporter]

This is very important for at least an issue of my interest: access to 
University-managed proxies which enable access to Editor-managed scientific 
journal archives. Indeed, apparently some editors, even if you are correctly 
recognised under the allowed provenance (a certain University) filter you out 
unless you use certain browsers. In my case, Wiley does not allow me in with 
Chrome (switchy manages auto proxy switching) but does with Firefox (FoxyProxy 
manages auto proxy switching). 

Original comment by marco.br...@gmail.com on 27 Aug 2011 at 2:33