public Builder proxyAuthentication(String proxyUserName, String proxyUserPassword) {
      builder.proxyAuthentication(proxyUserName, proxyUserPassword);
      return this;
    }
set authentication for proxy

@param proxyUserName username for proxy authentication
@param proxyUserPassword username for proxy authentication
@return Returns this builder for call chaining.
src/main/java/com/google/maps/GeoApiContext.java