Videos occasionally get stretched when in portrait mode

I often find that video podcasts are stretched while watching in portrait mode. There is no real reason why this happens, it just happens randomly and you should notice it by trying to open the fullscreen player a few times.

Steps to replicate:

- Open any video podcast, such as https://pca.st/xv3ffcz6
- Click on the video to make it full screen.
- If it does not show up stretched, try going back then clicking twice on the video or opening PiP, then opening the video in fullscreen.

Recording (issue visible from 0:13):

https://user-images.githubusercontent.com/16253818/183881681-55995200-67b8-45fe-a02c-efecfc8ae17f.mp4

Start by reproducing the stretching in the fullscreen player using the listed video podcast, portrait mode, back navigation, and PiP flows. Inspect the Android video-player entry points involved in fullscreen and PiP transitions. Done means repeated transitions no longer distort the video dimensions.

Written by the indexing model from the issue text.