chromium/third_party/blink/web_tests/http/tests/devtools/tracing/resources/timeline-iframe-with-style.html

<!DOCTYPE HTML>
<style>
    .testHolder > .red { background-color: red; }
    .testHolder > .green { background-color: green; }
    .testHolder > .blue { background-color: blue; }
    .testHolder > .snow { background-color: snow; }
    .testHolder > .red .dummy { }
    .testHolder > .green .dummy { }
    .testHolder > .blue .dummy { }
    .testHolder > .snow .dummy { }
</style>
<body>
    <div class="testHolder">
        <div id="testElementOne">One</div>
        <div id="testElementTwo">Two</div>
        <div id="testElementThree">Three!</div>
    </div>
</body>