WM_CLASS not set up correctly when running as native Wayland client

Summary

Tor Browser uses --class "Tor Browser" parameter to identify itself from plain Firefox windows, and this parameter doesn't work when running as native Wayland client. The windows class is firefox rather than expected Tor Browser.

Steps to reproduce:

1. Modify start-tor-browser script or start-tor-browser.deskktop entry to include MOZ_ENABLE_WAYLAND=1 environment variable, in order to prefer Wayland client
2. Put start-tor-browser.desktop into corresponding directory
3. Start Tor Browser

What is the current bug behavior?

Tor Browser is started as native Wayland client, but the icon is a generic Wayland icon instead of Tor Browser's own. Furthermore, under certain desktop environments, window grouping and start new instance doesn't work at all, because the running Tor Browser isn't identified / linked to the desktop entry.

What is the expected behavior?

The running Tor Browser should be linked to the desktop entry. Tor Browser should display its own icon, window grouping and start new instance should work. windows class should be Tor Browser.

Environment

• OS: Fedora Kinoite 36
• DE: KDE Plasma 5.24.5, Wayland session
• Software distribution: Downloaded directly from torproject.org (tor-browser-linux64-11.0.13_en-US.tar.xz)

This issue also occurs in unofficial distribution torbrowser-launcher, relevant issue

Relevant logs and/or screenshots

Wayland client

X11 client (under Wayland session, through XWayland)

A hotfix was implemented in !466 (closed)