Noticed this warning in the console on test.wikipedia.org (after saving an edit) while testing a patch for T193570 (probably unrelated).
Exception in load-callback in module schema.SaveTiming:
> Error: Module "ext.navigationTiming.rumSpeedIndex" is not loaded.
at require (load.php?...:171)
at getPaintTiming (<anonymous>:206:555)
at getNavTiming (<anonymous>:207:578)
at emitSaveTiming (<anonymous>:209:709)
Looks like we forgot about the second call-path to `getNavTiming()` when adding rumSpeedIndex, namely from `emitSaveTiming`, which while being called after the load starts for `preloadedModules`, does not wait for it (and shouldn't need to)
Its report rate hasn't changed significantly, but then again, wmf.2 is only on group0 still right now (test wikis). It probably wont' affect everybody though, it depends a particular cache state, in which the unrelated load for `preloadedModules` remains unresolved (cache miss or some version change), but `schema.SaveTiming` is cache-hit for emitSaveTiming. Within a warm cache scenario, this does indeed seem likely given that schema hasn't changed in years, whereas our other modules have.