code: public static String addProtocolIfMissing(final String aUrl, final String aProtocol) {
      if (aUrl != null && aUrl.startsWith("//")) {
        return aProtocol + aUrl;
      }
  
      return aUrl;
    }
docs: adds the protocol if missing.
  
  @param aUrl the url to check
  @param aProtocol the protocol to add
  @return the url including the protocol