Sometimes you need to use many different Proxy Auto Configuration files with a web browser, usually when testing or trying out new installation of the proxy servers. Most browsers have command line options that let you specify different PAC files to use which can then be configured so that you have multiple startup options.
The actual command line for starting Chrome on Mac OSX is
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome
add your own extensions for the PAC file as you need to.