chromium/third_party/blink/web_tests/external/wpt/css/css-contain/contain-layout-019.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Containment Test: Layout containment inside a fit-content element</title>
<link rel="help" href="https://crbug.com/1268449">
<link rel="help" href="https://drafts.csswg.org/css-contain-1/#containment-layout">
<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
<meta name=assert
    content="Layout containment inside a fit-content element should update size when the content is changed">
<style>
    #contain-parent {
        width: fit-content;
    }

    #contain-layout {
        contain: layout;
        background: green;
    }

    #content {
        width: 50px;
        height: 100px;
    }
</style>
<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<div id="contain-parent">
    <div id="contain-layout">
        <div id="content"></div>
    </div>
</div>

<script>
window.requestAnimationFrame(() => {
    document.body.offsetTop;
    document.getElementById('content').style.width = '100px';
    document.body.offsetTop;
});
</script>