public static ExtendedCell createCell(ExtendedCell cell, byte[] value, byte[] tags) {
    if (cell instanceof ByteBufferExtendedCell) {
      return new ValueAndTagRewriteByteBufferExtendedCell((ByteBufferExtendedCell) cell, value,
        tags);
    }
    return new ValueAndTagRewriteCell(cell, value, tags);
  }
Returns A new cell which is having the extra tags also added to it.
hbase-common/src/main/java/org/apache/hadoop/hbase/PrivateCellUtil.java