Code review comment for lp:~kdub/mir/fix-1626503

Looks good.

Nit:
+ for(auto it = onscreen_buffers.begin(); it != onscreen_buffers.end(); it++)
+ {
+ if (it->use_count == 0)
+ map->send_buffer(it->buffer->id());
+ }

Why not use a range-based for loop?