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

net/quic/core/quic_sent_packet_manager_interface.h

Index: net/quic/core/quic_sent_packet_manager_interface.h
diff --git a/net/quic/core/quic_sent_packet_manager_interface.h b/net/quic/core/quic_sent_packet_manager_interface.h
index d2bd0554bbb165e5aedeee4f8316fe014dbcff26..b1860e4d008f3a1b77df2ce546947d6e5e836224 100644
--- a/net/quic/core/quic_sent_packet_manager_interface.h
+++ b/net/quic/core/quic_sent_packet_manager_interface.h
@@ -7,6 +7,7 @@
 
 #include "base/macros.h"
 #include "net/base/net_export.h"
+#include "net/quic/core/congestion_control/send_algorithm_interface.h"
 #include "net/quic/core/quic_packets.h"
 #include "net/quic/core/quic_pending_retransmission.h"
 #include "net/quic/core/quic_sustained_bandwidth_recorder.h"
@@ -189,6 +190,10 @@ class NET_EXPORT_PRIVATE QuicSentPacketManagerInterface {
   // Signals to the congestion controller that the connection has no outstanding
   // data to send.
   virtual void OnApplicationLimited() = 0;
+
+  // Returns the currently used congestion control algorithm.  The manager
+  // retains the ownership of the algorithm.
+  virtual const SendAlgorithmInterface* GetSendAlgorithm() const = 0;
 };
 
 }  // namespace net