Media track ID visibility at BWE level

webrtc/video_send_stream.h

Index: webrtc/video_send_stream.h
diff --git a/webrtc/video_send_stream.h b/webrtc/video_send_stream.h
index 266112e5871550d9406a945981647724170d1bfa..11365c774505f9a015324022950f9e54ecb63ff5 100644
--- a/webrtc/video_send_stream.h
+++ b/webrtc/video_send_stream.h
@@ -202,6 +202,9 @@ class VideoSendStream {
     // Enables periodic bandwidth probing in application-limited region.
     bool periodic_alr_bandwidth_probing = false;
 
+    // Track ID as specified during track creation.
+    std::string track_id;
+
    private:
     // Access to the copy constructor is private to force use of the Copy()
     // method for those exceptional cases where we do use it.