Adding "adapter" ORTC objects on top of ChannelManager/BaseChannel/etc.

webrtc/pc/rtpreceiver.h

Index: webrtc/pc/rtpreceiver.h
diff --git a/webrtc/pc/rtpreceiver.h b/webrtc/pc/rtpreceiver.h
index c135f227c03a47adcfd7912fc249a5f71b29b5bf..ba17280f95f8609b4130dbf5379e191a7baf7722 100644
--- a/webrtc/pc/rtpreceiver.h
+++ b/webrtc/pc/rtpreceiver.h
@@ -34,6 +34,7 @@ namespace webrtc {
 class RtpReceiverInternal : public RtpReceiverInterface {
  public:
   virtual void Stop() = 0;
+  virtual uint32_t ssrc() const = 0;

[pthatcher1, 2017/02/09 00:11:44]

Can you leave a comment about what this is and why we need it?  I assume it's
used as an RtpReceiver ID of sorts, but that's not clear.

[Taylor Brandstetter, 2017/02/10 00:19:46]

Done.

 };
 
 class AudioRtpReceiver : public ObserverInterface,
@@ -41,8 +42,9 @@ class AudioRtpReceiver : public ObserverInterface,
                          public rtc::RefCountedObject<RtpReceiverInternal>,
                          public sigslot::has_slots<> {
  public:
-  AudioRtpReceiver(MediaStreamInterface* stream,
-                   const std::string& track_id,
+  // An SSRC of 0 will create a receiver that will match the first SSRC it
+  // sees.

[pthatcher1, 2017/02/09 00:11:44]

Instead of making a comment like this, could we do this?

1.  This constructor DCHECKs a non-zero SSRC.
2.  A different constructor doesn't take an SSRC and is clearly marked as the
"match the first SSRC it sees" type.

Also, what happens if you create more than one such receiver?  Is it random
which one "sees" the SSRC first?

[Taylor Brandstetter, 2017/02/10 00:19:46]

We could do that, I was just trying to change as few things as possible in this
CL; this comment is just documenting existing behavior. I'll leave a TODO.

+  AudioRtpReceiver(const std::string& track_id,
                    uint32_t ssrc,
                    cricket::VoiceChannel* channel);
 
@@ -74,6 +76,7 @@ class AudioRtpReceiver : public ObserverInterface,
 
   // RtpReceiverInternal implementation.
   void Stop() override;
+  uint32_t ssrc() const override { return ssrc_; }
 
   void SetObserver(RtpReceiverObserverInterface* observer) override;
 
@@ -99,8 +102,9 @@ class AudioRtpReceiver : public ObserverInterface,
 class VideoRtpReceiver : public rtc::RefCountedObject<RtpReceiverInternal>,
                          public sigslot::has_slots<> {
  public:
-  VideoRtpReceiver(MediaStreamInterface* stream,
-                   const std::string& track_id,
+  // An SSRC of 0 will create a receiver that will match the first SSRC it
+  // sees.
+  VideoRtpReceiver(const std::string& track_id,
                    rtc::Thread* worker_thread,
                    uint32_t ssrc,
                    cricket::VideoChannel* channel);
@@ -127,6 +131,7 @@ class VideoRtpReceiver : public rtc::RefCountedObject<RtpReceiverInternal>,
 
   // RtpReceiverInternal implementation.
   void Stop() override;
+  uint32_t ssrc() const override { return ssrc_; }
 
   void SetObserver(RtpReceiverObserverInterface* observer) override;