code: protected T build() {
          final T instance;
          try {
              instance = build(connection(), maxContentLength(),
                                       isValidateHttpHeaders(), isPropagateSettings());
          } catch (Throwable t) {
              throw new IllegalStateException("failed to create a new InboundHttp2ToHttpAdapter", t);
          }
          connection.addListener(instance);
          return instance;
      }
docs: Builds/creates a new {@link InboundHttp2ToHttpAdapter} instance using this builder's current settings.