<head>
<script>
if (window.testRunner)
        testRunner.dumpAsText();
</script>
</head>
This test passes if it doesn't crash.
<style id="style">
#elm::before, #elm::after { display:block; -webkit-column-span:all; content:".........."; }
:last-of-type { position: absolute;}
</style>
<div id="div" style="visibility:hidden; -webkit-columns:4; columns:4;">
   <span id="elm">&nbsp;</span>
</div>
<script>
document.execCommand("SelectAll");
var elem = document.getElementById("style");
elem.innerHTML="%a%b3%bf%5c";
</script>