classic mode and wayland

[Colin Walters <walters verbum org>]

Hi,

Currently GContinuous' smoketest-classic test often fails with:
http://build.gnome.org/continuous/buildmaster/builds/2016/05/10/42/smoketest-classic/work-gnome-continuous-x86_64-runtime/journal.txt

```
nautilus-classic.desktop: ** (nautilus-desktop:1030): WARNING **: Desktop icons only supported on X11. 
Desktop not created
gnome-session: gnome-session-binary[682]: WARNING: App 'nautilus-classic.desktop' respawning too quickly
gnome-session-binary: WARNING: App 'nautilus-classic.desktop' respawning too quickly
gnome-session-binary: Unrecoverable failure in required component nautilus-classic.desktop
```

It seems like this started with:
https://bugzilla.gnome.org/show_bug.cgi?id=746286

But it's now a bit more fatal for reasons I haven't investigated.

Is anyone looking at classic + Wayland?  I can just disable the test for now I guess,
or perhaps we could consider a slightly-less-classic mode that just doesn't draw
desktop icons?