public Builder requestMetricsReporter(RequestMetricsReporter requestMetricsReporter) {
      this.requestMetricsReporter = requestMetricsReporter;
      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