chromium/third_party/blink/web_tests/wpt_internal/printing/page-fitting-004-print.html

<!DOCTYPE html>
<link rel="match" href="page-fitting-004-print-ref.html">
<script>
  if (window.testRunner) {
    testRunner.setPrintingSize(300, 400);
    testRunner.setPrintingMargin(13);
    testRunner.setShouldCenterAndShrinkToFitPaper(true);
  }
</script>
<style>
  @page {
    size: 600px 800px;
    margin: 100px;
  }
  html {
    writing-mode: vertical-rl;
  }
  body {
    margin: 0;
    font-size: 3em;
    background: yellow;
  }
</style>
First page. The margins should be the same on every side.
<div style="break-before:page;">
  Second page. The margins should be the same on every side.
</div>