chromium/third_party/blink/web_tests/printing/page-orientation.html

<!DOCTYPE html>
<script>
  if (window.testRunner)
      testRunner.setPrinting();
</script>
<style>
  @page clockwise {
      page-orientation: rotate-right;
  }
  @page counter-clockwise {
      page-orientation: rotate-left;
  }
</style>
<div>
  A normal page.
</div>
<div style="page:clockwise;">
  This page is rotated clockwise.
</div>
<div style="page:counter-clockwise;">
  This page is rotated counter-clockwise.
</div>
<div>
  A normal page again.
</div>