Wire-up BWE feedback for audio receive streams.

webrtc/voice_engine/channel.cc

Index: webrtc/voice_engine/channel.cc
diff --git a/webrtc/voice_engine/channel.cc b/webrtc/voice_engine/channel.cc
index 48111dbb670fab6724bb99c7cef1c2492e662438..d16a595a2d512974078d3f7a3bf1833235c22963 100644
--- a/webrtc/voice_engine/channel.cc
+++ b/webrtc/voice_engine/channel.cc
@@ -2927,14 +2927,18 @@ void Channel::SetCongestionControlObjects(
     RtpPacketSender* rtp_packet_sender,
     TransportFeedbackObserver* transport_feedback_observer,
     PacketRouter* packet_router) {
-  RTC_DCHECK(feedback_observer_proxy_.get());
-  RTC_DCHECK(seq_num_allocator_proxy_.get());
-  RTC_DCHECK(rtp_packet_sender_proxy_.get());
   RTC_DCHECK(packet_router != nullptr || packet_router_ != nullptr);
-  feedback_observer_proxy_->SetTransportFeedbackObserver(
-      transport_feedback_observer);
-  seq_num_allocator_proxy_->SetSequenceNumberAllocator(packet_router);
-  rtp_packet_sender_proxy_->SetPacketSender(rtp_packet_sender);
+  if (transport_feedback_observer) {
+    RTC_DCHECK(feedback_observer_proxy_.get());
+    feedback_observer_proxy_->SetTransportFeedbackObserver(
+        transport_feedback_observer);
+  }
+  if (rtp_packet_sender) {
+    RTC_DCHECK(rtp_packet_sender_proxy_.get());
+    rtp_packet_sender_proxy_->SetPacketSender(rtp_packet_sender);
+  }
+  if (seq_num_allocator_proxy_.get())
+    seq_num_allocator_proxy_->SetSequenceNumberAllocator(packet_router);
   _rtpRtcpModule->SetStorePacketsStatus(rtp_packet_sender != nullptr, 600);
   if (packet_router != nullptr) {
     packet_router->AddRtpModule(_rtpRtcpModule.get());