chromium/third_party/blink/web_tests/fast/borders/border-radius-percent.html

<!doctype html>
<html>
<head>
<style type="text/css">
    p{
        text-align:center;
        background:#ccc;
        border-radius:50% 50% 0 0 / 100%;
        width:300px;
        height:150px;
    }
    p.all{
        border:1px solid #000;
    }
    p.bottom{
        border-bottom:1px solid #000;
    }
</style>
</head>
<body>
<p class="bottom">Corners on top should be rounded and a border of 1px black on the bottom.</p>
<p class="all">Corners on top should be rounded and a border of 1px black all around.</p>
</body>
</html>