public void merge(SearcherTimer other) {
            for (Map.Entry<Activity, Long> invokingEntry : other.invoking.entrySet()) {
                addInvoking(invokingEntry.getKey(), invokingEntry.getValue());
            }
            for (Map.Entry<Activity, Long> returningEntry : other.returning.entrySet()) {
                addReturning(returningEntry.getKey(), returningEntry.getValue());
            }
        }
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