chromium/third_party/blink/web_tests/wpt_internal/css/webkit-text-security/first-letter.html

<!doctype html>
<title>Do not apply ::first-letter to -webkit-text-security</title>
<link rel="match" href="first-letter-ref.html">
<style>
  #obfuscated { -webkit-text-security: circle; }
  #obfuscated::first-letter { font-size: 100px; }
</style>
<div id="obfuscated">PASS</div>