public long getAverageWaitTime() {
    final long completedRequests = getCompletedRequests();
    return completedRequests > 0 ? mSumOfWaitTime / completedRequests : 0;
  }
@return average wait time, that is sum of reported wait times divided by number of completed
    requests
samples/scrollperf/src/main/java/com/facebook/samples/scrollperf/instrumentation/PerfListener.java