MediaRecorder in detached contexts

[youennf]

As illustrated by https://jsfiddle.net/863njp7y/, MediaRecorder implementations do not agree in behavior of detached frames MediaRecorders. MediaRecorder.start is throwing with different errors (InvalidStateError, NotAllowedError, SecurityError) in tested browsers. MediaRecorder.stop is throwing in Chrome but not in Firefox and Safari. I did not try resume/pause but I guess they might have similar issues.

https://jsfiddle.net/q4t5sLnc/ checks MediaRecorder.state in that context. Firefox and Safari go to inactive while Chrome is keeping with recording.

[youennf]

There is a WPT test for MediaRecorder constructor which shows also differences between implementations: https://wpt.fyi/results/mediacapture-record/MediaRecorder-detached-context.html?label=experimental&label=master&aligned

[jan-ivar]

That WPT test which is passing in Chromium is not adhering to any spec:

assert_equals(err.name, 'NotAllowedError');

There's no mention of NotAllowedError in this spec, so we should probably take action some way or another on this issue.