private long getTime(Long storedTillNow) {
            long tillNow;
            if (storedTillNow == null) {
                tillNow = 0L;
            } else {
                tillNow = storedTillNow.longValue();
            }
            return tillNow;
        }
A container for storing time stamps throughout the lifetime of an Execution instance.

<p>Check state both when entering and exiting, to allow for arbitrary
new queries anywhere inside a search chain.

@author Steinar Knutsen
container-search/src/main/java/com/yahoo/search/statistics/TimeTracker.java