Simplify passing video codec factories in media engine

webrtc/media/engine/nullwebrtcvideoengine.h

Index: webrtc/media/engine/nullwebrtcvideoengine.h
diff --git a/webrtc/media/engine/nullwebrtcvideoengine.h b/webrtc/media/engine/nullwebrtcvideoengine.h
index 2fe87f4badb9348a0e2d26345bc2d2b5635c1e71..9c687b9db744ac85ca4366a0e2f17862c4532e41 100644
--- a/webrtc/media/engine/nullwebrtcvideoengine.h
+++ b/webrtc/media/engine/nullwebrtcvideoengine.h
@@ -33,31 +33,15 @@ class WebRtcVideoEncoderFactory;
 // CompositeMediaEngine.
 class NullWebRtcVideoEngine {
  public:
-  NullWebRtcVideoEngine() {}
-  ~NullWebRtcVideoEngine() {}
+  std::vector<VideoCodec> codecs() const { return std::vector<VideoCodec>(); }
 
-  void SetExternalDecoderFactory(WebRtcVideoDecoderFactory* decoder_factory) {}
-  void SetExternalEncoderFactory(WebRtcVideoEncoderFactory* encoder_factory) {}
-
-  void Init() {}
-
-  const std::vector<VideoCodec>& codecs() {
-    return codecs_;
-  }
-
-  RtpCapabilities GetCapabilities() {
-    RtpCapabilities capabilities;
-    return capabilities;
-  }
+  RtpCapabilities GetCapabilities() const { return RtpCapabilities(); }
 
   VideoMediaChannel* CreateChannel(webrtc::Call* call,
                                    const MediaConfig& config,
                                    const VideoOptions& options) {
     return nullptr;
   }
-
- private:
-  std::vector<VideoCodec> codecs_;
 };
 
 }  // namespace cricket