I wrote #90 before realizing "speaker" was removed in w3c/webappsec-permissions-policy#360 and in Chrome. @alvestrand what happened to it?

Concerns:

1. Without it, people may permission-escalate with allow="microphone" or allow="camera" in order to use this feature. While it's true you need those permissions today to use this feature in Chrome, this may not always be so. E.g. API to request audio output device selection #86
2. There's still a "speaker" permission. Without a corresponding feature-policy, it's unclear whether this feature is available in iframes by default or not (whether you have cam/mic or not).
3. It removed consent in iframes by default, which seemed desirable.

cc @alvestrand, @guidou, @achronop