<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-contain/#content-visibility">
<link rel="help" href="https://crbug.com/1197492">
<map>
  <ul></ul>
  <progress></progress>
  <iframe></iframe>
</map>
<style>
body, map, ul, progress {
    content-visibility: auto;
    height: 0vw;
  }
</style>
