This upstream Chromium browser test intermittently fails in Brave
builds due to the same root cause as the already-disabled
PageStabilityMetricsMinWaitTest.NetworkAndMainThreadIdleDelayed:
Brave's cosmetic filters inject a MutationObserver and setInterval
(500ms) polling on all pages, generating continuous renderer tasks
that prevent the IdlenessDetector's 500ms quiet window from completing
before the 4-second page stability timeout fires.
The test expects kNetworkAndMainThread outcome (bucket 1) but gets
kTimeout (bucket 5) because NetworkBecameIdle is never signaled.
Upstream flake rate is 1% over 30 days per LUCI Analysis. Not
disabled upstream. Brave modifications exist in the actor directory
via chromium_src but do not affect page stability monitoring.
Resolves https://github.com/brave/brave-browser/issues/54205
Netzenbot
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