nested-iframe-loading-another-iframe.html

<html>
<head>
    <style>body { background-color: yellow; }</style>
</head>
<body>
    <div>
        <p>Load another level of nested iframe.</p>
    </div>
    <iframe src="3rd-level-iframe-with-blocking-resource.php"></iframe>
</body>
</html>

chromium/third_party/blink/web_tests/http/tests/misc/resources/nested-iframe-loading-another-iframe.html