private void freeAllReferencedMobCells() throws IOException {
    for (MobCell cell : referencedMobCells) {
      cell.close();
    }
    referencedMobCells.clear();
  }
Firstly reads the cells from the HBase. If the cell are a reference cell (which has the
reference tag), the scanner need seek this cell from the mob file, and use the cell found from
the mob file as the result.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MobStoreScanner.java