fast/layers/layer-content-visibility-change.html

<div style="position: relative;">
    <div style="width: 100px; height: 100px; background-color: red;"></div>
    <div style="visibility: hidden; position: absolute; top: 0;">
        <div id="inner" style="width: 100px; height: 100px; background-color: green;"></div>
    </div>
</div>
<script>
    function test()
    {
        document.getElementById("inner").style.visibility = "visible";
    }
    if (window.testRunner) {
        document.body.offsetTop;
        testRunner.display();
        test();
    } else
        setTimeout(test, 0);
</script>