HTTP Trace is a chrome extension that replicates the functionality of the LiveHTTPHeaders plugin for Firefox.
I got the icon from here: http://openiconlibrary.sourceforge.net/gallery2/?./Icons/status/user-online-2.png
Original source: http://www.oxygen-icons.org/
Also check out:
- CloudFlare CDN Cache Monitor - https://github.com/xims/cf_cache_mon - Check cache status of loaded resources on the page.