<video>s gets increasingly smaller after entering and exiting fullscreen VR videos (reproducible on any site, including YouTube)

[MortimerGoro]

STR:

1. Load https://www.youtube.com/watch?v=sPyAQQklc1s
2. Enter Fullscreen
3. Enter 360 video projection
4. Exit video projection
5. Exit fullscreen
6. See Repeat step 2

[caseyyee]

This also happens with standard 2D YouTube content as well when Fullscreen. Does not seem to be an issue anywhere else.

[cvan]

1. Load test case #5 from https://webxr.sh/media
2. Click the video's Fullscreen icon to enter fullscreen
3. Change the Projection Mode (i.e., the VR Goggles icon)
4. Press the ← button in the Media/Transport Controls to exit
5. Re-enter with a new Projection Mode
6. Notice upon exiting again, the video gets exponentially smaller it seems

[caseyyee]

OK, so I noticed that with this, the window.innerWidth and Height is changing every fullscreen cycle:

1x 800x450
2x 980x551
3x 1296x729

window.outerWidth and Height remain at 800x450, and screen.width and screen.height also remain 1200x1200