<!DOCTYPE html>
<html>
<head>
  <script>
  if (window.testRunner)
    testRunner.dumpAsText();
    
  function dumpLayers()
  {
    var layersResult = document.getElementById('layers');
    if (window.testRunner)
      layersResult.innerText = window.internals.layerTreeAsText(document);
    
  }
  window.addEventListener('load', dumpLayers, false)
  </script>
</head>
<body>
  <div style="position: fixed; left: 0; top: 0; width:200px; height:200px;">
    <div style="position: absolute; left: -300px; width: 300px; height: 200px; background-color: blue;"></div>
  </div>
<pre id="layers">Layer tree goes here in DRT</pre>
</body>
</html>