HTTP Traffic Monitoring for Automated Testing

I would like to be able to monitor all the HTTP requests being made by a web page in an automated testing scenario.

I know how to drive browsers with Selenium.

Is there some kind of proxy that can be interacted with programatically. What would help is something that can be flagged to start recording all the HTTP requests then flagged to stop.

I believe FireFox has some proxy settings that can be driven from Selenium but Chrome is the highest priority browser for testing.

I have heard of BetaMax but think this is more about simulating and replaying REST calls rather than monitoring traffic programatically.