UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.84 Safari/537.36

Steps to reproduce the problem:
1. Open 'https://webrtc.github.io/samples/'
2. Click 'Clear browsing data' on chrome settings
3. Click 'Basic getUserMedia demo' in webrtc samples
4. An exception threw in 'getUserMedia' API

What is the expected behavior?

What went wrong?
can't reproduce when access the demo directly by paste link in a new tab
can't reproduce when click the demo link with ‘Ctrl’ key pressed

Did this work before? N/A 

Does this work in other browsers? N/A

Chrome version: 63.0.3239.84  Channel: n/a
OS Version: OS X 10.12.6
Flash Version: