The Tor Browser / file revision

 // tests third party cookie blocking using a favicon load directly from chrome.

 // in this case, the docshell of the channel is chrome, not content; thus

 // the cookie should be considered third party.

 function test() {

   waitForExplicitFinish();

   Services.prefs.setIntPref("network.cookie.cookieBehavior", 1);

   Services.obs.addObserver(function (theSubject, theTopic, theData) {

     var uri = theSubject.QueryInterface(Components.interfaces.nsIURI);

     var domain = uri.host;

     if (domain == "example.org") {

       ok(true, "foreign favicon cookie was blocked");

       Services.prefs.setIntPref("network.cookie.cookieBehavior", 0);

       Services.obs.removeObserver(arguments.callee, "cookie-rejected");

       finish();

     }

   }, "cookie-rejected", false);

   // kick off a favicon load

   gBrowser.setIcon(gBrowser.selectedTab, "http://example.org/tests/extensions/cookie/test/damonbowling.jpg");

 }