Is this always, or only after an unclean shutdown?  After a clean shutdown, these should be only a single stat() call that notices that the file doesn't exist; that shouldn't take 45ms.

Are there background threads at that time?

Also, aren't the stability metrics collected right at start-up, meaning that it would still block waiting for a background thread to complete?

This is the aggregate mean. Which means for runs where the function takes no time the value will be 0 but there's sufficient users who do take time in that function that it still averages out to 45ms per startup.

MetricsService::RecordCurrentStabilityHistograms no longer shows up in sampling profiler. Closing. (This makes sense because we no longer read files in that function.)