<!DOCTYPE html>

<html>
<head>
    <style>
        .video {
            position: absolute;
            left: 10px;
            top: 50px;
            height: 360px;
            width: 680px;
            background-color: black;
            will-change: transform;
        }
        
        .masker {
            position: absolute;
            left: 10px;
            top: 50px;
            height: 360px;
            width: 680px;
            border-top: 50px solid white;
            border-right: 300px solid white;
            border-bottom: 50px solid white;
            border-left: 300px solid white;
            box-sizing: border-box;
        }
    </style>
</head>
<body>
<p>Tests that the video frames of an HTMLVideoElement are black if no video MediaStreamTrack is enabled.</p>
<div class="video"></div>
<div class="masker"></div>

</body>
</html>