@Override
  public void updateMemStoreDeltaSizeHistogram(int memStoreDeltaSize) {
    if (memStoreDeltaSize >= 0) {
      incMemStoreSizeHistogram.add(memStoreDeltaSize);
    } else if (memStoreDeltaSize < 0) {
      decMemStoreSizeHistogram.add(-memStoreDeltaSize);
    }
  }
Hadoop2 implementation of MetricsHeapMemoryManagerSource. Implements BaseSource through
BaseSourceImpl, following the pattern
hbase-hadoop-compat/src/main/java/org/apache/hadoop/hbase/regionserver/MetricsHeapMemoryManagerSourceImpl.java