Reset the BWE when the network changes

webrtc/media/engine/webrtcvoiceengine.cc

Index: webrtc/media/engine/webrtcvoiceengine.cc
diff --git a/webrtc/media/engine/webrtcvoiceengine.cc b/webrtc/media/engine/webrtcvoiceengine.cc
index ae2518b73af9d74feed8a847d51c4f2f9b60ab9e..2f3ca99206ddda1583419a1762c9f2b88ad0ff29 100644
--- a/webrtc/media/engine/webrtcvoiceengine.cc
+++ b/webrtc/media/engine/webrtcvoiceengine.cc
@@ -2334,6 +2334,11 @@ void WebRtcVoiceMediaChannel::OnRtcpReceived(
   }
 }
 
+void WebRtcVoiceMediaChannel::OnBestConnectionChanged(

[stefan-webrtc, 2016/03/17 12:48:19]

What will happen when we're not using BUNDLE? It's probably not a good thing
that voice tears down the BWE if only the voice connection has changed.

[honghaiz3, 2016/03/23 19:55:40]

This is a very good point.
We are using one BWE for all media channels, right?
Then the choices are
1) reset BWE if one media connection's network changed, or 
2) reset BWE if all media connections's networks changed. 
Is option 2) better?
In most cases, the media connection should be using the same network anyway, so
option 1 and 2 may not have big differences. 

+    Connection* best_connection) {
+  call_->OnBestConnectionChanged(best_connection);
+}
+
 bool WebRtcVoiceMediaChannel::MuteStream(uint32_t ssrc, bool muted) {
   RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
   int channel = GetSendChannelId(ssrc);