Re: [mediacapture-screen-share] mute and unmute events of MediaStreamTrack should not be fired based on user non-action (#141)

The issue occurs when capturing "Your Entire Screen", "Application Window" or "Chromium Tab", not just "Chromium Tab". The video track simply abruptly goes mute in 4 seconds at Chromium 85.0.4173.0, where `inactive` event is still defined that event is fired. The `MediaStreamTrack` appears to be tied to some user activation scheme or algorithm, though per the specification should not be. Whether user action occurs or not `mute` event is eventually fired for no clear reason.

```
blob:https://run.plnkr.co/3371ff9b-c93e-4185-8ecc-714337f7da81
(index):31 blob:https://run.plnkr.co/b1904285-775d-412f-a76c-76305718d7f8
(index):32 Uncaught DOMException: Failed to execute 'stop' on 'MediaRecorder': The MediaRecorder's state is 'inactive'.
    at MediaRecorder.recorder.ondataavailable (https://run.plnkr.co/preview/ckbxq5ngg00072v6tkrwi1gcs/:32:22)
recorder.ondataavailable @ (index):32
(index):28 Event {isTrusted: true, type: "stop", target: MediaRecorder, currentTarget: MediaRecorder, eventPhase: 2, …}
(index):17 inactive
```

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