Setting environment variables for Gnome on Wayland session only

I'm testing GNOME 3.14 on Wayland on ArchLinux and I would also like to test GTK+ on Wayland. To do so, I can set the following two env variables from terminal

export GDK_BACKEND=wayland CLUTTER_BACKEND=wayland

anf then run my app (i.e. nautilus) from terminal too. However I would like to set this session-wide so that I don't have to launch my apps from terminal. I think I cannot set them on .bashrc because they will break my standard GNOME on X session.

So where is the proper place to set those variables for GNOME on Wayland session ONLY?