private void initBreakdown() {
        if (searcherTracking != null) {
            throw new IllegalStateException("initBreakdown invoked"
                    + " when measurement structures are already initialized.");
        }
        List<? extends Processor> searchers = searchChain.components();
        searcherTracking = new SearcherTimer[searchers.size()];
        for (int i = 0; i < searcherTracking.length; ++i) {
            searcherTracking[i] = new SearcherTimer(searchers.get(i).getId().stringValue());
        }
    }
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