@InterfaceAudience.Private
  protected RegionSizeCalculator createRegionSizeCalculator(RegionLocator locator, Admin admin)
    throws IOException {
    return new RegionSizeCalculator(locator, admin);
  }
Allows subclasses to initialize the table information.
@param connection The Connection to the HBase cluster. MUST be unmanaged. We will close.
@param tableName  The {@link TableName} of the table to process.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/TableInputFormatBase.java