Add a test that implicit submission is not allowed when the first sub…

…mit button is disabled. (#35385)

html/semantics/forms/form-submission-0/implicit-submission.optional.html

@@ -35,5 +35,13 @@
   assert_equals(event.submitter, null);
   assert_true(event instanceof SubmitEvent);
 }, 'Submit event with no submit button');
+
+promise_test(async (test) => {
+  let form = populateForm('<input name=text value=abc><input name=submitButton type=submit disabled>');
+  form.text.focus();
+  form.addEventListener('submit', test.unreached_func('submit event should not be dispatched'));
+  await test_driver.send_keys(form.text, ENTER);
+}, 'Submit event with disabled submit button');
+
 </script>
 </body>