Attach TransportFeedbackPacketLossTracker to ANA (PLR only)

webrtc/modules/congestion_controller/transport_feedback_adapter.h

Index: webrtc/modules/congestion_controller/transport_feedback_adapter.h
diff --git a/webrtc/modules/congestion_controller/transport_feedback_adapter.h b/webrtc/modules/congestion_controller/transport_feedback_adapter.h
index 616bebe00a03fd76b29f559835f1399bc8cbbbc9..bcbf16ab99dc9c635505a6529e3d187145e56684 100644
--- a/webrtc/modules/congestion_controller/transport_feedback_adapter.h
+++ b/webrtc/modules/congestion_controller/transport_feedback_adapter.h
@@ -21,6 +21,8 @@
 
 namespace webrtc {
 
+class TransportFeedbackAdapterObserver;
+
 namespace rtcp {
 class TransportFeedback;
 }  // namespace rtcp
@@ -30,7 +32,13 @@ class TransportFeedbackAdapter {
   explicit TransportFeedbackAdapter(const Clock* clock);
   virtual ~TransportFeedbackAdapter();
 
-  void AddPacket(uint16_t sequence_number,
+  void RegisterTransportFeedbackAdapterObserver(
+      TransportFeedbackAdapterObserver* observer);
+  void DeRegisterTransportFeedbackAdapterObserver(
+      TransportFeedbackAdapterObserver* observer);
+
+  void AddPacket(uint32_t ssrc,
+                 uint16_t sequence_number,
                  size_t length,
                  const PacedPacketInfo& pacing_info);
   void OnSentPacket(uint16_t sequence_number, int64_t send_time_ms);
@@ -59,6 +67,10 @@ class TransportFeedbackAdapter {
   std::vector<PacketFeedback> last_packet_feedback_vector_;
   uint16_t local_net_id_;
   uint16_t remote_net_id_;
+
+  rtc::CriticalSection observers_lock_;
+  std::vector<TransportFeedbackAdapterObserver*> observers_
+      GUARDED_BY(&observers_lock_);
 };
 
 }  // namespace webrtc