Intermittent TIMEOUT in /html/semantics/embedded-content/the-iframe-element/sandbox-top-navigation-same-site.tentative.sub.window.html

```
TIMEOUT [expected OK] /html/semantics/embedded-content/the-iframe-element/sandbox-top-navigation-same-site.tentative.sub.window.html

    TIMEOUT [expected FAIL] subtest: A same-site unsandboxed iframe navigation does not consume user activation and allows top-level navigation.

    Test timed out
```