Prevent a voice channel from sending data before a renderer is set.

webrtc/audio/audio_send_stream.cc

Index: webrtc/audio/audio_send_stream.cc
diff --git a/webrtc/audio/audio_send_stream.cc b/webrtc/audio/audio_send_stream.cc
index c18331cea6c21dc83766ee869585ec0e9a42437a..fa632b348d147adfa578dede5cb0c1845e5f4a4b 100644
--- a/webrtc/audio/audio_send_stream.cc
+++ b/webrtc/audio/audio_send_stream.cc
@@ -97,10 +97,16 @@ AudioSendStream::~AudioSendStream() {
 
 void AudioSendStream::Start() {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  ScopedVoEInterface<VoEBase> base(voice_engine());
+  int error = base->StartSend(config_.voe_channel_id);
+  RTC_DCHECK_EQ(0, error);

[the sun, 2016/03/07 21:24:53]

I don't think a DCHECK is appropriate here. There are many reasons why
VoEBase::StartSend() could fail - it enables the ADM for recording! So it should
be treated as a legitimate run-time condition, not a logic error. Thus, to
maintain the current logic, add a conditional log line here, just like the one
in pc/channel.cc which will never be triggered anyway, following this CL.

(same in Stop())

[Taylor Brandstetter, 2016/03/08 00:00:31]

Done.

 }
 
 void AudioSendStream::Stop() {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  ScopedVoEInterface<VoEBase> base(voice_engine());
+  int error = base->StopSend(config_.voe_channel_id);
+  RTC_DCHECK_EQ(0, error);
 }
 
 void AudioSendStream::SignalNetworkState(NetworkState state) {