chromium/third_party/blink/web_tests/external/wpt/paint-timing/fcp-only/fcp-opacity-descendant.html

<!DOCTYPE html>
<head>
<title>Performance Paint Timing Test: FCP due to ancestor opacity</title>
<style>
    #main {
        width: 100px;
        height: 100px;
        left: 0px;
        position: relative;
        top: 0;
    }

    #child {
        opacity: 0;
    }

    /* contentful and intermediate classes are defined in test_fcp script. */
    #main.contentful #child {
        opacity: 1;
    }

    #main.intermediate #child {
        opacity: 1;
    }

    #main.intermediate {
        opacity: 0;
    }

    #main.contentful {
        opacity: 0.5;
    }
</style>
</head>
<body>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../resources/utils.js"></script>
<div id="main">
    <div id="child">Text</div>
</div>
<script>
    test_fcp("First contentful paint fires due to its ancestor getting positive opacity.");
</script>
</body>
</html>