@Override
  public void updateIncrement(long t, long blockBytesScanned) {
    incrementHisto.add(t);
    if (blockBytesScanned > 0) {
      blockBytesScannedCount.incr(blockBytesScanned);
      incrementBlockBytesScanned.add(blockBytesScanned);
    }
  }
Hadoop2 implementation of MetricsRegionServerSource. Implements BaseSource through
BaseSourceImpl, following the pattern
hbase-hadoop-compat/src/main/java/org/apache/hadoop/hbase/regionserver/MetricsRegionServerSourceImpl.java