REGRESSION (iOS 15.1 beta): Blank video after backgrounding PWA and resuming video

• Component: WebRTC
• Status: RESOLVED CONFIGURATION CHANGED

[Virginia Farley]

This behavior can be seen on the by following the steps on this minimal test page: https://virginiafarley.github.io/samples/src/blank-video/

The steps to reproduce this bug are:

1. On iOS 15.1 beta, open the link https://virginiafarley.github.io/samples/src/blank-video/ in Safari
2. Create a PWA out of this link 
3. Click the "Capture canvas" button
4. Click the "Capture audio" button and allow microphone access when prompted
5. If video is not already playing, click "Play Video"
6. Switch to another application for 5-10 seconds
7. Return to the app and observe that the video state is paused
8. Click "Play Video" and observe that the video is blank while the video state is playing.  Note that the MediaStream is inactive at this point.

Expected behavior: After returning to the app and observing that the video is paused, clicking "Play Video" will resume the video.

Able to reproduce with iOS 15.1 beta. Unable to reproduce with iOS 15.0. No repro in Safari (without creating PWA).  Note that audio capture is required to reproduce since without it, video will still be in playing state when returning from backgrounding app.

[Radar WebKit Bug Importer]

<rdar://problem/84102916>

[Brent Fulgham]

This should now be fixed in iOS 15.2.