<!DOCTYPE html>
<html class="reftest-wait">
<head>
<style>
.flexContainer {
display: flex;
width: 300px;
height: 300px;
background: yellow;
}
.flexItem {
border: 1px dashed purple;
}
</style>
<script>
function finish() {
document.documentElement.removeAttribute('class');
}
</script>
</head>
<body onload="setTimeout(finish, 0)">
<div class="flexContainer">
<embed src="about:blank" class="flexItem"></embed>
</div>
</body>
</html>