overflow-iframe-enter-compositing.html

<html>
<head>
  <script src="../../resources/run-after-layout-and-paint.js"></script>
  <style>
    iframe {
      height: 150px;
      width: 150px;
    }
  </style>
  <script>
    if (window.internals) {
      internals.settings.setPreferCompositingToLCDTextEnabled(true);
    }
    function doTest()
    {
      if (window.testRunner)
        testRunner.waitUntilDone();
      runAfterLayoutAndPaint(function() {
        var iframe = document.getElementById("parent-iframe");
        var box = iframe.contentDocument.getElementById("box");
        box.setAttribute("style", "height:500px;width:500px;");
        iframe.contentDocument.body.offsetWidth; // See bug 41999
        if (window.testRunner) {
          testRunner.dumpAsText();
          document.getElementById('layertree').innerText = internals.layerTreeAsText(document);
          testRunner.notifyDone();
        }
      });
    }
    window.addEventListener("load", doTest, false);
  </script>
</head>
<body>
    <iframe id="parent-iframe" src="resources/subframe-small.html"></iframe>
    <pre id="layertree"></p>
</body>
</html>

chromium/third_party/blink/web_tests/compositing/force-compositing-mode/overflow-iframe-enter-compositing.html