The Tor Browser / file revision

 <?xml version="1.0"?>

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

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

 	class="reftest-wait">

 <hbox style="display: none">

   <bindings id="testBindings" xmlns="http://www.mozilla.org/xbl"

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

     <binding id="testBinding" >

       <content>

 	<xul:label value="anon label"/>

 	<children/>

       </content>

     </binding>

   </bindings>

 </hbox>

 <script>

 <![CDATA[

 var cont;

 window.onload = function() {

   const XUL_NS = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";

   cont = document.getElementById("container");

   for(var i=0; i<2; i++) {

     var item = document.createElementNS(XUL_NS, "button");

     cont.appendChild(item);

     item.label = i;

   }

   document.documentElement.getBoundingClientRect();

   var item = cont.firstChild;

   //alert(item.label);

   cont.insertBefore(item.nextSibling, item);

   document.documentElement.removeAttribute("class");

 }

 ]]>

 </script>

 <hbox id="container" style="-moz-binding: url('#testBinding');"/>

 </window>