[mediacapture-main] If getUserMedia access is not granted, devicechange event should only be fired if devices of a given type go from 0 to 1 or 1 to 0 (#690)

youennf has just created a new issue for https://github.com/w3c/mediacapture-main:

== If getUserMedia access is not granted, devicechange event should only be fired if devices of a given type go from 0 to 1 or 1 to 0 ==
Following on WebRTC meeting, we should make this additional requirement to limit the leakage of user plugging in/out devices while still allowing web page to track whether it can use getUserMedia.

Please view or discuss this issue at https://github.com/w3c/mediacapture-main/issues/690 using your GitHub account