Introduce struct MediaConfig, with construction-time settings.

webrtc/media/webrtc/nullwebrtcvideoengine.h

 /*
  * libjingle
  * Copyright 2016 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 50 matching lines @@
   const std::vector<VideoCodec>& codecs() {
     return codecs_;
   }
 
   RtpCapabilities GetCapabilities() {
     RtpCapabilities capabilities;
     return capabilities;
   }
 
   VideoMediaChannel* CreateChannel(webrtc::Call* call,
+      const MediaConfig& config,
       const VideoOptions& options) {
     return nullptr;
   }
 
  private:
   std::vector<VideoCodec> codecs_;
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_MEDIA_WEBRTC_NULLWEBRTCVIDEOENGINE_H_