Add AudioSendStream to Call.

webrtc/audio_send_stream.h

 /*
  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 28 matching lines @@
       std::string ToString() const;
 
       // Sender SSRC.
       uint32_t ssrc = 0;
 
       // RTP header extensions used for the received stream.
       std::vector<RtpExtension> extensions;
     } rtp;
 
     // Transport for outgoing packets.
     Transport* send_transport = nullptr;

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

if you could also explain ownership rules for this variable, that would be good.

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

Done.

 
     // Underlying VoiceEngine handle, used to map AudioSendStream to lower-level
     // components.
     // TODO(solenberg): Remove when VoiceEngine channels are created outside
     // 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.
   };
 
   virtual Stats GetStats() const = 0;
 };
 }  // namespace webrtc
 
 #endif  // WEBRTC_AUDIO_SEND_STREAM_H_