ensure wayland is used for chromium browsers

[joshleblanc]

I'm pretty sure this isn't the best way to do this, but with the v2 update, everything seemed to break if you weren't using chromium.

All this is doing is doing the same check we already do for valid browsers after finding the executable, and applying the wayland ozone platform if it's valid.

[dinvlad]

Oh was just about to make a PR for this! Much needed on Vivaldi. Atm, my workaround was to

ln -s ~/.config/chromium-flags.conf ~/.config/vivaldi-stable.conf

but yours is a nicer, more universal solution and doesn't "pollute" the config tree with yet another file.

[dhh]

I actually think we should just have the flags file there. That's the best way to control this flag and the rest of them. We have several in chromium-flags.conf.