<head>
    <title>Old title</title>
    <script type="text/javascript">
        setTimeout(function(){ document.title = "New title"; }, 3000);
    </script>
</head>

<body>
    <p>This page should change its title after 3s.</p>
    <p>When opening the :buffer completion ("gt"), the title should update while it's open.</p>
</body>