Add task queue to Call.

webrtc/config.h

Index: webrtc/config.h
diff --git a/webrtc/config.h b/webrtc/config.h
index b2dfe2d272642fa5b8f73bd4a0e75b4a3c4925d1..829485049ce6ef534a78ca556dcba9e0508bd7e7 100644
--- a/webrtc/config.h
+++ b/webrtc/config.h
@@ -124,12 +124,20 @@ struct VideoStream {
 };
 
 struct VideoEncoderConfig {
+ public:
   enum class ContentType {
     kRealtimeVideo,
     kScreen,
   };
 
+  VideoEncoderConfig& operator=(VideoEncoderConfig&&) = default;
+  VideoEncoderConfig& operator=(const VideoEncoderConfig&) = delete;
+
+  // Mostly used by tests.  Avoid creating copies if you can.
+  VideoEncoderConfig Copy() const { return VideoEncoderConfig(*this); }
+
   VideoEncoderConfig();
+  VideoEncoderConfig(VideoEncoderConfig&&) = default;
   ~VideoEncoderConfig();
   std::string ToString() const;
 
@@ -144,6 +152,11 @@ struct VideoEncoderConfig {
   // unless the estimated bandwidth indicates that the link can handle it.
   int min_transmit_bitrate_bps;
   bool expect_encode_from_texture;
+
+ private:
+  // Access to the copy constructor is private to force use of the Copy()
+  // method for those exceptional cases where we do use it.
+  VideoEncoderConfig(const VideoEncoderConfig&) = default;
 };
 
 // Controls the capacity of the packet buffer in NetEq. The capacity is the