mozilla-release/widget/tests/window_bug593307_offscreen.xul

<?xml version="1.0"?>
<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
<window title="Mozilla Bug 593307"
  width="100" height="100"
  onload="onLoad();"
  xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">

  <script type="application/javascript"
          src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js" />

<body xmlns="http://www.w3.org/1999/xhtml" id="body">
</body>

<script class="testbody" type="application/javascript">
<![CDATA[

var centerscreen = null;
var SimpleTest = window.arguments[0];
var finish = window.arguments[1];

function onLoad()
{
  centerscreen = window.openDialog('window_bug593307_centerscreen.xul','', 'chrome,centerscreen,dependent,dialog=no');
}

function finished() {
  centerscreen.close();
  finish();
}

]]>
</script>

</window>