I always want to know how the resource inspection work in webkit/safari/chrome\'s WebInspector work.
The browser must provide a native BPI or something for javascrip
The resource requests and other DevTools/WebInspector related data is collecting by InspectorController and it's agents. (it just C++ code)
After that all the data is pushing into WebInspector as JS calls of WebInspector object's methods.
As you probably know all the DevTools/WebInspector's GUI is an html page and a lot of JavaScript.
You can try to investigate the internal world of Inspector by Inspector itself.
All the traffic between Inspector and inspected page are passing via two functions: from Inspector to inspected page - sendMessageToBackend from inspected page to Inspector - devtools$$dispatch
You can track the latest changes for WebInspector in WebKit via this link.