While the person sharing the screen in a Google Meet meeting has the impression that it works (and test pages like https://mozilla.github.io/webrtc-landing/gum_test.html leave the same impression), participants only see a blank page.

Reproducible: Always

Steps to Reproduce:
1. Ensure that the latest Firefox version is installed from Fedora's repos
sudo dnf install --refresh firefox

2. Start/join a Google Meet meeting twice in two windows/tabs in Firefox
3. Start the presentation, choosing either a window or the entire screen
4. Observe that the presenter sees its own shared info, but not the other(s).

5. Downgrade Firefox to the release version from Fedora's repos
sudo dnf list --showduplicates firefox
sudo dnf install firefox-119.0-2.fc39.x86_64

6. Go through steps 2 and 3 and observe the difference 
7. To make sure it's about Fedora's Firefox build use Mozilla's for the same test
https://www.mozilla.org/en-US/firefox/download/thanks/