The Tor Browser / file revision

 <?xml version="1.0" encoding="UTF-8" ?>

 <?xml-stylesheet href="chrome://global/skin/" type="text/css"?>

 <window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"

         onload="setTimeout(runTest, 0)">

   <vbox>

     <text value="powered by example.com" style="padding: 16px;"/>

   </vbox>

   <hbox id="t" style="position: fixed; right: 16px; bottom: 16px;">

     <button label="OK"/>

   </hbox>

 <script><![CDATA[

 var SimpleTest = window.opener.wrappedJSObject.SimpleTest;

 var SpecialPowers = window.opener.wrappedJSObject.SpecialPowers;

 var is = window.opener.wrappedJSObject.is;

 var ok = window.opener.wrappedJSObject.ok;

 // We run this off a setTimeout from onload, because the XUL window

 // only does its intrinsic-height layout after the load event has

 // finished

 function runTest() {

   var t = document.getElementById("t");

   var tBottom = t.getBoundingClientRect().bottom;

   is(tBottom, document.documentElement.getBoundingClientRect().bottom - 16,

      "check fixed-pos element t bottom positioned correctly");

   ok(tBottom < 200, "fixed-pos element t bottom must be sane, less than 200 (got " + tBottom + ")");

   window.close();

   SimpleTest.finish();

 }

 ]]></script>

 </window>