code: public static String getCanonicalCountry(String tzid) {
          String country = getRegion(tzid);
          if (country != null && country.equals(kWorld)) {
              country = null;
          }
          return country;
      }
docs: Return the canonical country code for this tzid.  If we have none, or if the time zone
  is not associated with a country or unknown, return null.