Code review comment for lp:~vanvugt/mir/managed-surface

I've tried to outline in improved-tiling-window-management MR some of the ways I'd like to see the architecture improve and how we can really get the window manager as an elegant controller. In light of being convinced it's fatally flawed, I am definitely inclined to lean towards continue working on the controller based approach than add this surface wrapper.

I hate to feel like I am repeating myself a fourth or fifth time on the same topic but I will try and summarize my thoughts again for the benefit of EU/AUS time discussion:

1. Model-View-Controller is a well known and understood pattern which has several additional benefits for us: Decoupling of model object (e.g.) surface from interface used to control it, and an easier way to store intra-surface state.
2. As I've outlined in the tiling-window-management MR I think untangling the controller may be able to provide a significant simplification to our current factory interfaces and the path from session mediator to scene.