Predicate

I notice now that this code assumes that the zeroth element of `LatencyBrackets` corresponds to the median, or more generally that `LatencyBrackets[i]` either doesn't exist in a given `RoundTripStats` or always corresponds to the same quantile. This isn't clearly implied by a reading of the `RoundTripStats` type definition. Can you add a comment about that here or there or both?