void pruneOldRegionReports() {
    final long now = EnvironmentEdgeManager.currentTime();
    final long pruneTime = now - regionReportLifetimeMillis;
    final int numRemoved = quotaManager.pruneEntriesOlderThan(pruneTime, this);
    if (LOG.isTraceEnabled()) {
      LOG.trace("Removed " + numRemoved + " old region size reports that were older than "
        + pruneTime + ".");
    }
  }
Removes region reports over a certain age.
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/QuotaObserverChore.java