Specify MediaStreamTrack support speech recognition behavior if muted = true

[beaufortfrancois]

When #118 was merged, it was unspecified whether the HTMLMediaElement muted and MediaStreamTrack muted properties would change anything regarding speech recognition started with a MediaStreamTrack. I believe it should not impact it.

In Chromium sadly, audio is no longer rendered to the sink and thus is no longer transcribed if the volume of the media drops to 0. See code source. Shall we update Chromium or the spec?

FYI @evanbliu

[padenot]

It's very useful to mute an element and have it transcribed, from my point of view.

[beaufortfrancois]

FYI Chromium implementation has been updated to render muted audio if it's rendering audio from a media stream. See https://chromium-review.googlesource.com/c/chromium/src/+/6198929 and https://wpt.fyi/results/mediacapture-fromelement/capture-muted.html?label=experimental&label=master&aligned

Thank you @evanbliu!

[evanbliu]

Because the media stream spec already specifies that muted audio should continue to render, I don't think we need to explicitly state that again in the Web Speech spec. I'll close out this issue now since the issue is fixed in Chromium, but feel free to reopen if anyone objects!