Allow congestion controller state to be accessed by the debug visitors.

net/quic/core/quic_multipath_sent_packet_manager.h

Index: net/quic/core/quic_multipath_sent_packet_manager.h
diff --git a/net/quic/core/quic_multipath_sent_packet_manager.h b/net/quic/core/quic_multipath_sent_packet_manager.h
index 7f2e73f662468c76c1962321ae4e18923156d8c5..b5162480313ee04b310ce70d4197aa3c28157fd0 100644
--- a/net/quic/core/quic_multipath_sent_packet_manager.h
+++ b/net/quic/core/quic_multipath_sent_packet_manager.h
@@ -167,6 +167,8 @@ class NET_EXPORT_PRIVATE QuicMultipathSentPacketManager
 
   void OnApplicationLimited() override;
 
+  const SendAlgorithmInterface* GetSendAlgorithm() const override;
+
  private:
   friend class test::QuicConnectionPeer;
   friend class test::QuicMultipathSentPacketManagerPeer;