<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<bindings xmlns="http://www.mozilla.org/xbl">
  <binding id="x"><content><span>a
b<children xmlns="http://www.mozilla.org/xbl"/></span></content></binding>
</bindings>
<style>
  div#d {
    white-space: pre;
    -moz-binding: url(#x);
  }
  span#s {
    display: inline-block;
  }
</style>
<script>
function boom()
{
  document.getElementById("s").style.display = "inline";
}
</script>
</head>
<body onload="boom();">
  <div id="d"><span id="s">s</span></div>
</body>
</html>