<script>
function test() {
    if (window.internals)
        internals.settings.setSimpleLineLayoutDebugBordersEnabled(true);
    var target = document.getElementById("target");
    eventSender.mouseMoveTo(target.offsetLeft + 5, target.offsetTop + 5);
}
</script>
<body onload="test()">
<div id="target">This text should have border around it indicating it is in simple line layout mode</div>