LayoutTests/fast/text/mark-matches-overflow-clip.html

<style>
p {
    display: inline-block;
    overflow: scroll;
    width: 60px;
    margin: 50px;
}
</style>
<p>
<span style="position: relative; left: -25pt;">Quo usque tandem abutere, Catilina, patientia nostra?</span>
</p>
<script>
window.onload = function () {
    if (!window.internals) {
        document.write("This test requires internals + testRunner to run.");
        return;
    }

    testRunner.dumpAsText();
    internals.countMatchesForText("tandem", [], "mark");
    
    var markedNode = document.getElementsByTagName("span")[0].firstChild;
    document.write(internals.dumpMarkerRects("TextMatch"));
}
</script>