@Override
  protected boolean nextRow(ScannerContext scannerContext, Cell curRowCell) throws IOException {
    assert super.joinedContinuationRow == null : "Trying to go to next row during joinedHeap read.";
    this.storeHeap.seekToPreviousRow(PrivateCellUtil.createFirstOnRow(curRowCell));
    resetFilters();
    // Calling the hook in CP which allows it to do a fast forward
    if (this.region.getCoprocessorHost() != null) {
      return this.region.getCoprocessorHost().postScannerFilterRow(this, curRowCell);
    }
    return true;
  }
ReversibleRegionScannerImpl extends from RegionScannerImpl, and is used to support reversed
scanning.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ReversedRegionScannerImpl.java