paint-containment-as-formatting-context.html

<!DOCTYPE html>
<style>
div {
    height: 100px;
    width: 100%;
}
.container {
    contain: paint;
    border: 1px solid black;
}
.overhangingContainer {
    height: 10px;
}
.overhangingFloat {
    float: left;
}
</style>
<body>
<div class="overhangingContainer"><div class="overhangingFloat"></div></div>
<div class="container" data-offset-y=108></div>
<script src="../../../resources/check-layout.js"></script>
<script>
checkLayout(".container");
</script>

chromium/third_party/blink/web_tests/fast/css/containment/paint-containment-as-formatting-context.html