Intermittent failure in /html/semantics/forms/form-submission-0/jsurl-form-submit.tentative.html

```
OK /html/semantics/forms/form-submission-0/jsurl-form-submit.tentative.html

    FAIL [expected PASS] subtest: Verifies that form submissions scheduled inside javascript: urls take precedence over the javascript: url's return value.

    assert_equals: expected "/html/semantics/forms/form-submission-0/resources/form.html" but got "blank"
```