protected void setTableRecordReader(TableRecordReader tableRecordReader) {
    this.tableRecordReader = tableRecordReader;
  }
Allows subclasses to set the {@link TableRecordReader}. to provide other
{@link TableRecordReader} implementations.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapred/TableInputFormatBase.java