void update(byte[] encodedRegionName, Set<byte[]> families, long sequenceid,
    final boolean lowest) {
    Long l = Long.valueOf(sequenceid);
    this.highestSequenceIds.put(encodedRegionName, l);
    if (lowest) {
      ConcurrentMap<ImmutableByteArray, Long> m = getOrCreateLowestSequenceIds(encodedRegionName);
      for (byte[] familyName : families) {
        m.putIfAbsent(ImmutableByteArray.wrap(familyName), l);
      }
    }
  }
We've been passed a new sequenceid for the region. Set it as highest seen for this region and
if we are to record oldest, or lowest sequenceids, save it as oldest seen if nothing currently
older.
@param lowest Whether to keep running account of oldest sequence id.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceIdAccounting.java