chromium/third_party/blink/web_tests/http/tests/eventsource/resources/request-non-existent-eventsource-error.html

<html>
  <body>
    <script>
      function statusTest() {
        var source = new EventSource("does_not_exist");
        source.onerror = function() {
          top.finish();
        }
      }
      statusTest();
    </script>
  </body>
</html>