Code review comment for lp:~albaguirre/mir/fix-1475571

If it really is the GBM_BO_USE_SCANOUT flag making the difference, then wouldn't it be a better idea to fix the allocator to not try to allocate a scanout buffer for screencasts (which doesn't make sense anyway).

I'd be concerned that just dropping the check will instead bite us later when we try and scanout from a BO that's not scanout-capable.