Add AudioSendStream to Call.

webrtc/audio_send_stream.h

Index: webrtc/audio_send_stream.h
diff --git a/webrtc/audio_send_stream.h b/webrtc/audio_send_stream.h
index 2fb288f7abb67dd47ba445877573215798766ae8..03cf0f0478c387863d919742149dd042d56def17 100644
--- a/webrtc/audio_send_stream.h
+++ b/webrtc/audio_send_stream.h
@@ -54,7 +54,9 @@ class AudioSendStream : public SendStream {
     // of Call.
     int voe_channel_id = -1;
 
-    rtc::scoped_ptr<AudioEncoder> encoder;
+    // Ownership of the encoder object is transferred to Call when the config is
+    // passed to Call::CreateAudioSendStream().
+    AudioEncoder* encoder = nullptr;

[tommi, 2015/10/14 13:21:18]

I'm having a hard time understanding how the comment explains this encoder
variable and why it should not be a scoped_ptr.  Does ownership ever lie with
Config?  How is the objects lifetime and this pointer's value synchronized?
(I.e. how do we guarantee that we never use dangling pointers?)

[the sun, 2015/10/14 14:25:24]

The config is *copied* into webrtc::internal::AudioSendStream, so a scoped_ptr
can't be used, unless swapping the whole config into the AudioSendStream, which
might not be a bad idea, although currently a bit different from how it's done
for video.

[tommi, 2015/10/14 14:49:28]

I see... is it copied into the internal one then?  Would it make sense to hold
the Config itself as a scoped_ptr and pass ownership via Pass() instead of
copying?

[the sun, 2015/10/15 12:56:06]

Not clearcut what is the best approach here. I decided to comment out for now
and make the final decision when we get to actual use that part of the config
struct. I'm with you 100% that ownership should be explicit and fail safe.

     int cng_payload_type = -1;  // pt, or -1 to disable Comfort Noise Generator.
     int red_payload_type = -1;  // pt, or -1 to disable REDundant coding.
   };