Codebase Browser
chromium
Go to App

chromium/third_party/blink/web_tests/fast/multicol/focus-outline.html 

<!DOCTYPE html>
<p style="height:200px;">There should be a square-shaped outline
    below, probably with rounded borders.</p>
<div style="outline:auto; columns:3; column-gap:0; width:75px; column-fill:auto; height:100px;">
    <div style="height:400px;"></div>
</div>