bug#50773: ungoogled-chromium fails to use webcam

[Ludovic Courtès]

Hello!

As of commit c582be4c38596a6a31a39c6799723dcd8b6eb909 (Sept. 23),
ungoogled-chromium fails to grab images from my webcam (for instance in
BigBlueButton instances), printing this message repeatedly:

  [4685:3:0924/102919.814053:ERROR:video_stream_encoder.cc(1762)] Failed to 
encode frame. Error code: -7

I found that an older generation (Aug. 30) works for me:

  guix time-machine --commit=f91ae9425bb385b60396a544afe27933896b8fa3 -- \
    environment --ad-hoc ungoogled-chromium -- chromium

The regression must have been in between these two commits.

Thoughts?

Ludo’.