Based on my understanding of our discussions on error handling, NavigatorUserMediaError should inherit from DOMError to use the behavior of the object as defined in the DOM spec.

Also, I think the names of errors in DOMError are camel-cased rather than uppercase (uppercase names were used to define constants matching integer values assigned to the deprecated code attribute); so the errors for getUserMedia should be "PermissionDenied" and "ConstraintNotSatisfied".

I don't think these values should be defined as an enum — that doesn't bring us anything, and it doesn't align with what the DOM spec does (nor other APIs AFAICT); instead, the prose should simply say which errors get raised in what conditions.