chromium/third_party/blink/web_tests/external/wpt/css/css-contain/contain-body-overflow-002.html

<!doctype html>
<html lang=en class="reftest-wait">
<meta charset=utf-8>
<title>CSS-contain test: paint containment on body prevents overflow propagation</title>
<link rel="author" title="Florian Rivoal" href="https://florian.rivoal.net">
<meta name="assert" content="paint containment on body prevents overflow propagation">
<link rel="match" href="reference/contain-body-overflow-001-ref.html">
<link rel="help" href="https://drafts.csswg.org/css-contain-1/#contain-property">
<style>
html, body, p, div {
    margin: 0;
    width: 200px;
    height: 200px;
}
div { background: red; }
body {
    overflow: hidden;
    contain: paint;
}
:focus {
    outline: none;
}
</style>

<div></div>
<p tabindex=1 id=target>Test passes if there is no red.
<script>
window.onload = function() {
    document.getElementById("target").focus();
    setTimeout(() => {
        document.documentElement.className = "";
    }, 0);
}
</script>