Intermittent FAIL in /xhr/xhr-timeout-longtask.any.html, /xhr/xhr-timeout-longtask.any.worker.html

```
  ▶ Unexpected subtest result in /xhr/xhr-timeout-longtask.any.html:
  │ FAIL [expected PASS] Long tasks should not trigger load timeout
  └   → assert_unreached: [object ProgressEvent] Reached unreachable code
```