[mediacapture-output] setSinkId does not abort substeps

domenic has just created a new issue for 
https://github.com/w3c/mediacapture-output:

== setSinkId does not abort substeps ==
Per the algorithm given, "If sinkId does not match any audio output 
device identified by enumerateDevices()," then the promise will be 
rejected, but then the steps will proceed. You should add "and abort 
these substeps" to all such cases where you don't want to proceed.

Please view or discuss this issue at 
https://github.com/w3c/mediacapture-output/issues/42 using your GitHub
 account