The Tor Browser / file revision

 /* Any copyright is dedicated to the Public Domain.

  * http://creativecommons.org/licenses/publicdomain/  */

 // check that the second node under the document element is a PI with the

 // specified .target and .data

 function checkDOM(target, data) {

   // assume there are no whitespace nodes in XUL

   var piNode = document.documentElement.childNodes[1];

   if (!piNode || piNode.nodeType != Node.PROCESSING_INSTRUCTION_NODE ||

       piNode.target != target || piNode.data != data) {

     document.documentElement.style.backgroundColor = "red";

   }

 }