Attach TransportFeedbackPacketLossTracker to ANA (PLR only)

webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h

Index: webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h
diff --git a/webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h b/webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h
index ab9fc401674140a65cdb99066a1de40cfea47e08..7a562e54775d69b61069fdbc402a068cdf8f6919 100644
--- a/webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h
+++ b/webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h
@@ -337,13 +337,28 @@ struct PacketFeedback {
   PacedPacketInfo pacing_info;
 };
 
+// TODO(elad.alon): After the current TransportFeedbackObserver becomes obsolete
+// and is removed, use that name for this observer instead.
+// Background: The only implementers of this interface are
+// CongestionController and TransportFeedbackProxy.
+// CongestionController uses it to expose only a small subset of its
+// capabilities.
+// TransportFeedbackProxy is a temporary solution which exists to allow passing
+// the CongestionController down at a later stage.
+// Ideally, we'd get rid of this altogether, exposing CC. This will be done
+// after the order-of-creation issues have been resolved, and
+// TransportFeedbackProxy therefore removed. Then, we'll remove
+// TransportFeedbackAdapterObserver, reuse the name
+// TransportFeedbackObserver for TransportFeedbackAdapterObserver, and only
+// have one observer.
 class TransportFeedbackObserver {
  public:
   TransportFeedbackObserver() {}
   virtual ~TransportFeedbackObserver() {}
 
   // Note: Transport-wide sequence number as sequence number.
-  virtual void AddPacket(uint16_t sequence_number,
+  virtual void AddPacket(uint32_t ssrc,
+                         uint16_t sequence_number,
                          size_t length,
                          const PacedPacketInfo& pacing_info) = 0;
 
@@ -352,6 +367,16 @@ class TransportFeedbackObserver {
   virtual std::vector<PacketFeedback> GetTransportFeedbackVector() const = 0;
 };
 
+// See TODO above TransportFeedbackObserver for explanation of the difference
+// between these two.
+class TransportFeedbackAdapterObserver {
+ public:
+  virtual ~TransportFeedbackAdapterObserver() = default;
+
+  virtual void OnPacketAdded(uint32_t ssrc, uint16_t seq_num) = 0;
+  virtual void OnTransportFeedback(const rtcp::TransportFeedback& feedback) = 0;
+};
+
 class RtcpRttStats {
  public:
   virtual void OnRttUpdate(int64_t rtt) = 0;