[mediacapture-main] echo cancellation scope (#577)

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

== echo cancellation scope ==
In reference to [echo cancellation definition](https://w3c.github.io/mediacapture-main/#def-constraint-echoCancellation), it should be removing the sound being played. Now, [some browsers](https://bugs.chromium.org/p/chromium/issues/detail?id=954937) considers only sound being played from Webrtc remote peers for echo cancellation and not from the sound being played from other sources such as Web Audio API.

I think it is desired that all sounds being played should be considered for echo cancellation. If this is not the general case, then should there be an option in specifications for users to choose scope?

Please view or discuss this issue at https://github.com/w3c/mediacapture-main/issues/577 using your GitHub account