private void updateCounters() {
    ScanMetrics scanMetrics = scanner.getScanMetrics();
    if (scanMetrics == null) {
      return;
    }

    updateCounters(scanMetrics, numRestarts, context, numStale);
  }
If hbase runs on new version of mapreduce, RecordReader has access to counters thus can update
counters based on scanMetrics. If hbase runs on old version of mapreduce, it won't be able to
get access to counters and TableRecorderReader can't update counter values.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/TableRecordReaderImpl.java