  void acceptXdsConnection() {
    AssertionResult result = // xds_connection_ is filled with the new FakeHttpConnection.
        fake_upstreams_[0]->waitForHttpConnection(*dispatcher_, xds_connection_);
    RELEASE_ASSERT(result, result.message());
    result = xds_connection_->waitForNewStream(*dispatcher_, xds_stream_);
    RELEASE_ASSERT(result, result.message());
    xds_stream_->startGrpcStream();
    verifyGrpcServiceMethod();
  }
  void acceptXdsConnection() {
    AssertionResult result =  
        fake_upstreams_[0]->waitForHttpConnection(*dispatcher_, xds_connection_);
    RELEASE_ASSERT(result, result.message());
    result = xds_connection_->waitForNewStream(*dispatcher_, xds_stream_);
    RELEASE_ASSERT(result, result.message());
    xds_stream_->startGrpcStream();
    verifyGrpcServiceMethod();
  }