Hook up libjingle WebRtcVoiceEngine to Call API for combined A/V BWE.

BUG=4574,3109
R=pbos@webrtc.org, tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/49269004

Cr-Commit-Position: refs/heads/master@{#9150}
diff --git a/talk/session/media/channel.h b/talk/session/media/channel.h
index 14dae3b..441fe64 100644
--- a/talk/session/media/channel.h
+++ b/talk/session/media/channel.h
@@ -526,6 +526,11 @@
   ~VideoChannel();
   bool Init();
 
+  // downcasts a MediaChannel
+  virtual VideoMediaChannel* media_channel() const {
+    return static_cast<VideoMediaChannel*>(BaseChannel::media_channel());
+  }
+
   bool SetRenderer(uint32 ssrc, VideoRenderer* renderer);
   bool ApplyViewRequest(const ViewRequest& request);
 
@@ -559,12 +564,6 @@
   // Configuration and setting.
   bool SetChannelOptions(const VideoOptions& options);
 
- protected:
-  // downcasts a MediaChannel
-  virtual VideoMediaChannel* media_channel() const {
-    return static_cast<VideoMediaChannel*>(BaseChannel::media_channel());
-  }
-
  private:
   typedef std::map<uint32, VideoCapturer*> ScreencastMap;
   struct ScreencastDetailsData;