Restarting channel when swapping AudioReceiveStreams in WebrtcVoE.

BUG=webrtc:6346

Review-Url: https://codereview.webrtc.org/2383143002
Cr-Commit-Position: refs/heads/master@{#14493}
diff --git a/webrtc/media/engine/webrtcvoiceengine.cc b/webrtc/media/engine/webrtcvoiceengine.cc
index 358c142..71803cb 100644
--- a/webrtc/media/engine/webrtcvoiceengine.cc
+++ b/webrtc/media/engine/webrtcvoiceengine.cc
@@ -1424,6 +1424,7 @@
       LOG(LS_INFO) << "Stopping playout for channel #" << channel();
       stream_->Stop();
     }
+    playout_ = playout;
   }
 
  private:
@@ -1444,6 +1445,7 @@
     RTC_DCHECK(!stream_);
     stream_ = call_->CreateAudioReceiveStream(config_);
     RTC_CHECK(stream_);
+    SetPlayout(playout_);
   }
 
   rtc::ThreadChecker worker_thread_checker_;
@@ -1452,6 +1454,7 @@
   // The stream is owned by WebRtcAudioReceiveStream and may be reallocated if
   // configuration changes.
   webrtc::AudioReceiveStream* stream_ = nullptr;
+  bool playout_ = false;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(WebRtcAudioReceiveStream);
 };