Adding an accessor for https://github.com/envoyproxy/envoy/pull/18694

gfe-relnote: adding an accessor.
PiperOrigin-RevId: 405507053

quic/core/quic_session.h

diff --git a/quic/core/quic_session.h b/quic/core/quic_session.h
index 8789526..bacb4c1 100644
--- a/quic/core/quic_session.h
+++ b/quic/core/quic_session.h
@@ -789,6 +789,11 @@
   // streams.
   QuicStream* GetActiveStream(QuicStreamId id) const;
 
+  const UberQuicStreamIdManager& ietf_streamid_manager() const {
+    QUICHE_DCHECK(VersionHasIetfQuicFrames(transport_version()));
+    return ietf_streamid_manager_;
+  }
+
  private:
   friend class test::QuicSessionPeer;