Bug 1033885 - rename error to onFailure in code before introducing an actual error object r=jesup
Bug 1033885 - add MediaStreamError interface. r=jesup,bz
Bug 1033885 - return MediaStreamError instead of error strings, to spec. r=bz, r=jesup
Bug 1033885 - add mediaDevices.getUserMedia with promises. r=bz, r=jesup
Bug 1033885 - tests for mediaDevices.getUserMedia. r=drno