Just this morning I setup a greasemonkey script to rewrite those URLs to a local webserver (things like ajax.googleapis.com serving things like jquery). Pages load faster now too. Very limited, but works in many cases:
// ==UserScript==
// @name localize ajax googleapis
// @version 1
// @grant none
// @run-at document-start
var scripts = document.getElementsByTagName("script");
for (i=0; i<scripts.length; i++) {
var parent = scripts[i].parentElement;
var url = new URL(scripts[i].src);
if (url.host === "ajax.googleapis.com") {
url.host = "ajax.googleapis.com.local";
var newscript = document.createElement("script");
newscript.type="text/javascript";
newscript.src = url;
parent.insertBefore(newscript, scripts[i]);
parent.removeChild(scripts[i]);
console.log("Rewrote url as " + url);
}
}
// ==/UserScript==