LayoutTests/fast/css/rect-shadow-tiled.html

<style>
    .roundedRect {
        position: absolute;
        left: 100px;
        top: 100px;
        width: 320px;
        height: 250px;
        -webkit-border-radius: 100px;
        -webkit-box-shadow: 0 0 100px black;
     }
</style>
<div class="roundedRect"></div>