gecko-dev/dom/xml/resources/XMLPrettyPrint.xml

<?xml version="1.0"?>
<!-- This Source Code Form is subject to the terms of the Mozilla Public
   - License, v. 2.0. If a copy of the MPL was not distributed with this
   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->

<bindings xmlns="http://www.mozilla.org/xbl"
          xmlns:html="http://www.w3.org/1999/xhtml">

  <binding id="prettyprint" bindToUntrustedContent="true">

    <content><html:div id="top"/>
      <html:span style="display: none;"><children/></html:span>
    </content>

    <handlers>
      <handler event="prettyprint-dom-created" allowuntrusted="false">
        <![CDATA[
          document.getAnonymousNodes(this).item(0).appendChild(event.detail);
        ]]>
      </handler>
    </handlers>

  </binding>

</bindings>