UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/63.0.3239.84 Chrome/63.0.3239.84 Safari/537.36

Steps to reproduce the problem:
1. go to https://webrtc.github.io/samples/src/content/peerconnection/pc1/
2. open chrome://webrtc-internals
3. make a call
4. replace the senders video track with the null track like this:
var sender = pc1.getSenders()[1];
sender.replaceTrack(null);

What is the expected behavior?
chrome://webrtc-internals shows replaceTrack is used *somehow*, potentially by showing which track id/kind is replaced and with what track (or the null track)

What went wrong?
replaceTrack doesn't show up

Did this work before? No 

Does this work in other browsers? N/A

Chrome version: 63.0.3239.84  Channel: n/a
OS Version: 
Flash Version: