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);

[the sun, 2015/12/22 00:14:14]

Since we are relying on the channel only being used for either of send and
receive, and there being nothing to prevent the same channel id from being
specified in the Config for AudioReceive/SendStreams, it would be good to have
DCHECKs here to cover the expected cases:

1. internal objects null && all arguments non-null
2. internal objects null && packet router non-null
3. internal objects all non-null && all arguments null
4. packet_router_ non null && all arguments null

...if it is possible to write that in a way which isn't atrocious...

[stefan-webrtc, 2016/01/07 13:43:41]

I think it's non-trivial to test those without knowing if the channel is used
for sending or receiving. That is currently unknown and I'd prefer not wiring up
something like that for this cl.

What I can check is that if all members are null, then at least the
packet_router parameter should not be null. Since we allow calling with null on
all parameters even if SetCongestionControlObjects() weren't called in the
constructor of AudioReceiveStream, we can't check that some of the members are
non-null when all parameters are null. Not sure if it's worth adding getters to
all proxies just to be able to do this one DCHECK though?

-  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());