private long absoluteTime(Activity kind) {
        long elapsed = 0L;

        if (tracks.isEmpty()) {
            return 0L;
        }
        for (TimeTracker track : tracks) {
            elapsed += fetcher(kind, track);
        }
        return elapsed;
    }
Give an estimate on how much of the time tracked by this
instance was used fetching document contents. This will
by definition be smaller than last() - first().
container-search/src/main/java/com/yahoo/search/statistics/ElapsedTime.java