Codebase Browser
chromium
Go to App

chromium/third_party/blink/web_tests/http/tests/notifications/resources/iframe-display-permission.html 

<!doctype html>
<html>
  <head>
    <title>Notifications: Displays the current permission level.</title>
  </head>
  <body>
    <script>
      document.write(Notification.permission);
    </script>
  </body>
</html>