i mean as far as I can tell I would just have to write OpenXRSession.h/OpenXRSession.cpp in gfx/vr/service and include all the OpenXR stuff in there and get it all to build nicely
but it's definitely possible I think. would maybe have even happened already if mozilla never laid off all their xr staff. Maybe now in 2022 it'd be an openxr-backed browser with webxr support just like chrome, hell maybe even with linux support too
of course now that I look at OpenVRSession.cpp it's almost 1500 lines so maybe saying I'd "just" have to write it is underselling it a bit