<!DOCTYPE html>
<html>
<head>
<style>
.backdrop {
    position: absolute;
    height: 100px;
    width: 100px;
    background: green;
}
</style>
</head>
<body>
Test ::backdrop used in descendant selectors. The test passes if there are two green boxes and no red.
<div class="backdrop" style="top: 100px; left: 100px"></div>
<div class="backdrop" style="top: 100px; left: 300px"></div>
</body>
</html>