List<KeyValueScanner> getSnapshotScanners() {
    return Collections.singletonList(new SnapshotSegmentScanner(this));
  }
We create a new {@link SnapshotSegmentScanner} to increase the reference count of
{@link MemStoreLABImpl} used by this segment.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/ImmutableSegment.java