Attach TransportFeedbackPacketLossTracker to ANA (PLR only)

webrtc/modules/congestion_controller/transport_feedback_adapter.cc

Index: webrtc/modules/congestion_controller/transport_feedback_adapter.cc
diff --git a/webrtc/modules/congestion_controller/transport_feedback_adapter.cc b/webrtc/modules/congestion_controller/transport_feedback_adapter.cc
index ddffa7219692be1580bb64046779a245bcdb3c79..74181bfda448f8d982ada24af17f9b91e64f2077 100644
--- a/webrtc/modules/congestion_controller/transport_feedback_adapter.cc
+++ b/webrtc/modules/congestion_controller/transport_feedback_adapter.cc
@@ -36,19 +36,51 @@ TransportFeedbackAdapter::TransportFeedbackAdapter(const Clock* clock)
       local_net_id_(0),
       remote_net_id_(0) {}
 
-TransportFeedbackAdapter::~TransportFeedbackAdapter() {}
+TransportFeedbackAdapter::~TransportFeedbackAdapter() {
+  RTC_DCHECK(observers_.empty());
+}
+
+void TransportFeedbackAdapter::RegisterTransportFeedbackAdapterObserver(
+    TransportFeedbackAdapterObserver* observer) {

[the sun, 2017/03/22 12:06:42]

Please add thread checkers to document multithread usage in these functions.
We'd like to move away from a world full of locks to one where we know which
threads touch what data.

[elad.alon_webrtc.org, 2017/03/22 14:34:47]

We've tried that before with this class -
https://codereview.webrtc.org/2710213003/ - but ran into UT problems. We decided
that in this case, it wouldn't be worth the trouble.

+  rtc::CritScope cs(&observers_lock_);
+  RTC_DCHECK(observer);
+  RTC_DCHECK(std::find(observers_.begin(), observers_.end(), observer) ==
+             observers_.end());
+  observers_.push_back(observer);
+}
+
+void TransportFeedbackAdapter::DeRegisterTransportFeedbackAdapterObserver(
+    TransportFeedbackAdapterObserver* observer) {
+  rtc::CritScope cs(&observers_lock_);
+  RTC_DCHECK(observer);
+  const auto it = std::find(observers_.begin(), observers_.end(), observer);
+  RTC_DCHECK(it != observers_.end());
+  observers_.erase(it);
+  RTC_DCHECK(std::find(observers_.begin(), observers_.end(), observer) ==
+             observers_.end());

[stefan-webrtc, 2017/03/22 12:03:01]

This seems redundant to me. Should be enough to check that we only add an
observer once and that it exists when we remove it.

[minyue-webrtc, 2017/03/22 12:14:48]

I suggested it. It is clearly redundant, but just an extra dcheck, in case
observers_ is touched at other place than Register...

I am fine if you strongly advice removing it.

[elad.alon_webrtc.org, 2017/03/22 14:34:47]

Waiting for further input.

[the sun, 2017/03/23 11:11:14]

Agree that we don't need to unit test std::vector::erase() here.

[elad.alon_webrtc.org, 2017/03/23 13:37:30]

Removed.

+}
 
-void TransportFeedbackAdapter::AddPacket(uint16_t sequence_number,
+void TransportFeedbackAdapter::AddPacket(uint32_t ssrc,
+                                         uint16_t sequence_number,
                                          size_t length,
                                          const PacedPacketInfo& pacing_info) {
-  rtc::CritScope cs(&lock_);
-  if (send_side_bwe_with_overhead_) {
-    length += transport_overhead_bytes_per_packet_;
+  {
+    rtc::CritScope cs(&lock_);
+    if (send_side_bwe_with_overhead_) {
+      length += transport_overhead_bytes_per_packet_;
+    }
+    const int64_t creation_time_ms = clock_->TimeInMilliseconds();
+    send_time_history_.AddAndRemoveOld(
+        PacketFeedback(creation_time_ms, sequence_number, length, local_net_id_,
+                       remote_net_id_, pacing_info));
+  }
+
+  {
+    rtc::CritScope cs(&observers_lock_);
+    for (auto observer : observers_) {
+      observer->OnPacketAdded(ssrc, sequence_number);
+    }
   }
-  const int64_t creation_time_ms = clock_->TimeInMilliseconds();
-  send_time_history_.AddAndRemoveOld(
-      PacketFeedback(creation_time_ms, sequence_number, length, local_net_id_,
-                     remote_net_id_, pacing_info));
 }
 
 void TransportFeedbackAdapter::OnSentPacket(uint16_t sequence_number,
@@ -154,6 +186,12 @@ std::vector<PacketFeedback> TransportFeedbackAdapter::GetPacketFeedbackVector(
 void TransportFeedbackAdapter::OnTransportFeedback(
     const rtcp::TransportFeedback& feedback) {
   last_packet_feedback_vector_ = GetPacketFeedbackVector(feedback);
+  {
+    rtc::CritScope cs(&observers_lock_);
+    for (auto observer : observers_) {
+      observer->OnNewTransportFeedbackVector(last_packet_feedback_vector_);
+    }
+  }
 }
 
 std::vector<PacketFeedback>