Align with the Media Capture and Streams specification. NavigatorUserMediaError is out and MediaStreamError [1] is its replacement. [1] http://w3c.github.io/mediacapture-main/archives/20150324/getusermedia.html#mediastreamerror
There are still some uncertainties around MediaStreamError in the spec. Waiting for things to clear up.
MediaStreamError has been removed from the Media Capture and Streams specification.