@Override
    public void handleDuplicateStartKeys(HbckRegionInfo r1, HbckRegionInfo r2) throws IOException {
      byte[] key = r1.getStartKey();
      // dup start key
      errors.reportError(HbckErrorReporter.ERROR_CODE.DUPE_STARTKEYS,
        "Multiple regions have the same startkey: " + Bytes.toStringBinary(key), getTableInfo(),
        r1);
      errors.reportError(HbckErrorReporter.ERROR_CODE.DUPE_STARTKEYS,
        "Multiple regions have the same startkey: " + Bytes.toStringBinary(key), getTableInfo(),
        r2);
    }
Returns descriptor common to all regions. null if are none or multiple!
hbase-server/src/main/java/org/apache/hadoop/hbase/util/HbckTableInfo.java