void updateValueSize(final Result r, final long latency) throws IOException {
      if (r == null || (latency == 0)) return;
      int size = 0;
      // update replicaHistogram
      if (r.isStale()) {
        replicaLatencyHistogram.update(latency / 1000);
        numOfReplyFromReplica++;
      }
      if (!isRandomValueSize()) return;

      for (CellScanner scanner = r.cellScanner(); scanner.advance();) {
        size += scanner.current().getValueLength();
      }
      updateValueSize(size);
    }
Note that all subclasses of this class must provide a public constructor that has the exact
same list of arguments.
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/PerformanceEvaluation.java