<!DOCTYPE html>
<body>
<div id="top" style="overflow: scroll; height: 500px; width: 500px; background-color: blue">
  <div id="middle" style="position: absolute; height: 400px; width: 400px; background-color: green">
    <div id="child" style="position: relative; height: 300px; width: 300px; background-color: yellow; backface-visibility: hidden"></div>
  </div>
  <div id="tall" style="position: relative; height: 5000px; width: 20px; background-color: salmon"></div>
</div>
<div style="height: 5000px; width: 20px; background-color: papayawhip"></div>
<script>
if (window.testRunner) {
    internals.settings.setPreferCompositingToLCDTextEnabled(true);

    testRunner.dumpAsText();
    testRunner.setCustomTextOutput(
        internals.layerTreeAsText(document, internals.LAYER_TREE_INCLUDES_CLIP_AND_SCROLL_PARENTS));
}
</script>