<?xml version="1.0"?>

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

<hbox style="display: none">
<bindings xmlns="http://www.mozilla.org/xbl"
          xmlns:xul="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">

  <binding id="test" extends="xul:button">
  </binding>

</bindings>
</hbox>

<hbox style="display: block">
  <div style="-moz-binding: url(#test); width: 0; display: block;
              overflow: hidden; padding: 10px; border: 1px solid black; "
       xmlns="http://www.w3.org/1999/xhtml">Correct</div>
</hbox>
</window>