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

net/quic/core/quic_multipath_sent_packet_manager.cc

Index: net/quic/core/quic_multipath_sent_packet_manager.cc
diff --git a/net/quic/core/quic_multipath_sent_packet_manager.cc b/net/quic/core/quic_multipath_sent_packet_manager.cc
index 12ce5dfc45c11b1ac1e47e921956e1fa545cdac8..87010370a6b89130e5bbbac9d1321043ba5cc69b 100644
--- a/net/quic/core/quic_multipath_sent_packet_manager.cc
+++ b/net/quic/core/quic_multipath_sent_packet_manager.cc
@@ -521,4 +521,14 @@ void QuicMultipathSentPacketManager::OnApplicationLimited() {
   }
 }
 
+const SendAlgorithmInterface* QuicMultipathSentPacketManager::GetSendAlgorithm()
+    const {
+  QuicSentPacketManagerInterface* path_manager =
+      MaybeGetSentPacketManagerForActivePath(kDefaultPathId);
+  if (path_manager == nullptr) {
+    return nullptr;
+  }
+  return path_manager->GetSendAlgorithm();
+}
+
 }  // namespace net