default long incMemStoreSize(MemStoreSize delta) {
    return incMemStoreSize(delta.getDataSize(), delta.getHeapSize(), delta.getOffHeapSize(),
      delta.getCellsCount());
  }
Returns The new dataSize ONLY as a convenience
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MemStoreSizing.java