@Override
  public synchronized void setDone(ExtendedCellScanner cellScanner) {
    if (done) {
      return;
    }
    done = true;
    this.cellScanner = cellScanner;
  }
Returns One-shot cell scanner (you cannot back it up and restart)
hbase-client/src/main/java/org/apache/hadoop/hbase/ipc/HBaseRpcControllerImpl.java