Spec should define what the empty string (aka default device) means?

[youennf]

This would be good to add in HTMLMediaElement.setSkinId.
And would be useful for AudioContext.setSinkId as well.

Current proposal is to consider that the empty string means as if setSinkId was not called in the first place.
It usually means that audio will be played on the default device, with rerouting if the default device changes.