<!DOCTYPE html>
<html>
<style>
    body { margin: 0; }

    #layer {
        position: absolute;
        top: 100px;
        left: 100px;
        width: 200px;
        height: 200px;

        will-change: opacity;

        box-shadow: 0 0 20px black;
    }

    #button {
        display: inline-block;
        width: 100px;
        height: 100px;
        background-color: green;
        cursor: pointer;
        border-radius: 10px;
    }
</style>
<body>
<div id="layer">
    <div id="button" onclick="click()"></div>
</div>

<pre id="results"></pre>
<script>
if (window.testRunner)
    testRunner.dumpAsText();

window.onload = function () {
    if (window.internals)
       results.textContent = internals.layerTreeAsText(document, internals.LAYER_TREE_INCLUDES_EVENT_REGION | internals.LAYER_TREE_INCLUDES_ROOT_LAYER_PROPERTIES);
};
</script>
</body>
</html>
