Split out dscp option from VideoOptions to new struct MediaChannelOptions.

talk/media/webrtc/nullwebrtcvideoengine.h

Index: talk/media/webrtc/nullwebrtcvideoengine.h
diff --git a/talk/media/webrtc/nullwebrtcvideoengine.h b/talk/media/webrtc/nullwebrtcvideoengine.h
index 8af83a8ab1310163f37d93e673d1fa7204d25c5c..aa57bfd5f64234bba224b762f1f877d9cbd60cb7 100644
--- a/talk/media/webrtc/nullwebrtcvideoengine.h
+++ b/talk/media/webrtc/nullwebrtcvideoengine.h
@@ -68,7 +68,8 @@ class NullWebRtcVideoEngine {
   }
 
   VideoMediaChannel* CreateChannel(webrtc::Call* call,
-      const VideoOptions& options) {
+                                   const MediaChannelOptions& options,
+                                   const VideoOptions& video_options) {
     return nullptr;
   }