wk-testhunter shows the test started to timeout at: r250649 NOERROR r250650 UNKNOWN [r250651-r250652] TIMEOUT (Expected: PASS) within that range r250651 ([GTK][WPE] Enable async scrolling) seems the likely cause, although r250650 ([Nicosia] Enable runtime checks and triggers for async non-main-frame scrolling) might be right candidate. I tried to bisect the cause for the regression but I couldn't.
Very rarely this tests passes. Marking it as flaky timeout.