chromium/third_party/blink/web_tests/external/wpt/css/css-sizing/div-orthogonal-auto-margin-ref.html

<!DOCTYPE HTML>
<title> Ensure element is centered by auto margin for orthogonal writing mode </title>
<style>
  div {
    inset: 0;
    background-color: black;
    writing-mode: vertical-rl;
    margin: auto;
    position: absolute;
    block-size: 200px;
    inline-size: 100px;
    border: 5px solid red;
  }
</style>
<div></div>