Code review comment for lp:~raof/mir/dont-tear-down-compositor-if-unnecessary

+ virtual bool configuration_will_preserve_display_buffers(DisplayConfiguration const& conf) const = 0;

While not an issue in the current usage I worry that this style invites racy code. I would prefer something that's obviously atomic:

 bool apply_configuration_if_it_preserves_display_buffers(DisplayConfiguration const& conf) const = 0;