Method sendHeaders

xds/src/test/java/io/grpc/xds/DataPlaneRule.java:143–147

(Metadata responseHeaders)

        return next.startCall(new SimpleForwardingServerCall<ReqT, RespT>(call) {
          @Override
          public void sendHeaders(Metadata responseHeaders) {
            responseHeaders.merge(headersToReturn);
            super.sendHeaders(responseHeaders);
          }

          @Override
          public void close(Status status, Metadata trailers) {