[webrtc-pc] Constrainable properties on remote tracks are under-specified (#2121)

jan-ivar has just created a new issue for https://github.com/w3c/webrtc-pc:

== Constrainable properties on remote tracks are under-specified ==
What behaviors specific to remote peer connection tracks are available through the constraints APIs? There's a [single paragraph](https://w3c.github.io/webrtc-pc/#mediatracksupportedconstraints-mediatrackcapabilities-mediatrackconstraints-and-mediatracksettings) on the topic, and it doesn't say.

From @guidou in https://github.com/w3c/webrtc-pc/issues/2109#issuecomment-470566522, Chrome appears to have implemented something, so we should probably specify it, like we did in https://github.com/w3c/mediacapture-screen-share/issues/31. Otherwise, the next question might be why don't we support [whiteBalanceMode](https://w3c.github.io/mediacapture-image/#dom-mediatracksettings-whitebalancemode)?

Discuss.


Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/2121 using your GitHub account