Hm, could you sanity-check src/debug/gdk-event-latency-tracker.cpp for
me? As far as I can tell it is correct, but maybe there is some weird
issue. If you're seeing actual latencies that high, there should be
noticable lag in the UI during that time.
(The latency is estimated, since we don't have access to the actual
event clock and must guess at it, but the code is intended to try to
underestimate latency, not overestimate it...)