<!DOCTYPE html>
<p>There should be nothing below.</p>
<div style="-webkit-columns:6; -webkit-column-gap:0; width:4em; overflow:hidden;">
    <div style="-webkit-column-span:all; padding-left:4em;">
        <!-- column-span:all inside column-span:all has no effect. -->
        <div style="-webkit-column-span:all;">
            FAIL
        </div>
    </div>
</div>