Add TransportFeedback adapter, adapting remote feedback to bwe estiamtor

webrtc/modules/rtp_rtcp/interface/rtp_rtcp_defines.h

Index: webrtc/modules/rtp_rtcp/interface/rtp_rtcp_defines.h
diff --git a/webrtc/modules/rtp_rtcp/interface/rtp_rtcp_defines.h b/webrtc/modules/rtp_rtcp/interface/rtp_rtcp_defines.h
index 7642285caf152967f8a57542a2ea9803c35b6d55..8f3500ef1a5ada74eabacddfbf82645f26894030 100644
--- a/webrtc/modules/rtp_rtcp/interface/rtp_rtcp_defines.h
+++ b/webrtc/modules/rtp_rtcp/interface/rtp_rtcp_defines.h
@@ -24,6 +24,9 @@
 #define TIMEOUT_SEI_MESSAGES_MS 30000   // in milliseconds
 
 namespace webrtc {
+namespace rtcp {
+class TransportFeedback;
+}
 
 const int kVideoPayloadTypeFrequency = 90000;
 
@@ -293,15 +296,42 @@ class RtcpBandwidthObserver {
   virtual ~RtcpBandwidthObserver() {}
 };
 
-class SendTimeObserver {
+struct PacketInfo {
+  PacketInfo(int64_t arrival_time_ms,
+             int64_t send_time_ms,
+             uint16_t sequence_number,
+             size_t payload_size,
+             bool was_paced)
+      : arrival_time_ms(arrival_time_ms),
+        send_time_ms(send_time_ms),
+        sequence_number(sequence_number),
+        payload_size(payload_size),
+        was_paced(was_paced) {}
+  // Time corresponding to when the packet was received. Timestamped with the
+  // receiver's clock.
+  int64_t arrival_time_ms;
+  // Time corresponding to when the packet was sent, timestamped with the
+  // sender's clock.
+  int64_t send_time_ms;
+  // Packet identifier, incremented with 1 for every packet generated by the
+  // sender.
+  uint16_t sequence_number;
+  // Size of the packet excluding RTP headers.
+  size_t payload_size;
+  // True if the packet was paced out by the pacer.
+  bool was_paced;
+};
+
+class TransportFeedbackObserver {
  public:
-  SendTimeObserver() {}
-  virtual ~SendTimeObserver() {}
+  TransportFeedbackObserver() {}
+  virtual ~TransportFeedbackObserver() {}
+
+  // Note: Transport-wide sequence number as sequence number. Arrival time
+  // must be set to 0.
+  virtual void OnPacketSent(const PacketInfo& info) = 0;
 
-  // Transport-wide sequence number and timestamp (system time in milliseconds),
-  // of when the packet was put on the wire.
-  virtual void OnPacketSent(uint16_t transport_sequence_number,
-                            int64_t send_time) = 0;
+  virtual void OnTransportFeedback(const rtcp::TransportFeedback& feedback) = 0;
 };
 
 class RtcpRttStats {