chromium/third_party/blink/web_tests/fast/css/first-letter-set-text.html

<style>
    #target { font-family: Ahem; font-size: 50px; background-color: green; height: 50px; width: 50px; }
    #target:first-letter { color: red; }
</style>
<div id="target">Lorem</div>
<script>
    var target = document.getElementById("target");
    target.offsetTop;
    var text = target.firstChild;
    target.innerHTML = "ipsum";
    target.removeChild(target.firstChild);
</script>