As you may already know, chrome does not have a proxy management interface and it uses the system's proxy settings for that. If you want to change those settings from an extension you need to develop a plugin which communicates with NPAPI in order to apply settings.
I need such a plugin which will work on all major platforms (linux, windows, mac) and both on x86, x64 based systems. I only need two functions exposed so it should be fairly simple for a C++ programmer to get into the basics and build them.
getCurrentProxy - will return the current proxy set into the browser/system respectively:
1. ip address
3. protocol (http, socks4, socks5)
setProxy (ip_address, port, protocol) - will set the system proxy based on the parameters received. Will also validate the ip_address to be a valid ip, port to be a numerical value between 2 and 5 digits and protocol must be in the list: (http, socks4, socks5)
As a help to get you started you may read:
[url removed, login to view] - chrome guide on adding npapi plugins
http://www.firebreath.org/display/documentation/FireBreath+Home - NPAPI framework
Any questions, just ask.