<html>
<head>
    <style type="text/css" media="screen">
        iframe {
          border: 1px solid black;
          background-color: white;
        }
    </style>
    <script type="text/javascript">
        function test()
        {
            if (window.internals)
                internals.settings.setFrameFlattening("FullyEnabled")
            // Force synchronous layout.
            document.body.offsetHeight;
        }
    </script>
</head>
<body onload="test()">
    <style>body { background-color: green; }</style>

    <p><iframe width="500px" height="400px" src="resources/intermediate-frame.html">
</body>
</html>