<!DOCTYPE html>
<html>
<style>
.math {
    display: inline-flex;
}
.math > * {
    padding-bottom: 0.35em;
}
.mfrac {
    display: inline-flex;
    flex-direction: column;
}
.mfrac > :first-child {
    margin-block-end: 0.2em;
}
.mfrac > :last-child {
    margin-block-start: 0.2em;
}
.x {
    line-height: 9px;
}
.y {
    line-height: 12px;
}
</style>
<script>
if (window.testRunner)
    testRunner.dumpAsText();
</script>
<p>This test passes if it does not crash.</p>
<div class=math>
    <div class=mfrac>
        <div class=mfrac>
            <div class=x>x</div>
            <div class=y>y</div>
        </div>
        <div class=mfrac>
            <div class=mfrac>
                <div class=x>x</div>
                <div class=y>y</div>
            </div>
            <div class=x>z</div>
        </div>
    </div>
</div>
</html>