Code review comment for lp://qastaging/~afrantzis/mir/client-surface-buffering-mode

*Needs discussion*

It *would* be more flexible for the client to be able to borrow multiple buffers. The simplifications Kevin mentions look pretty enticing.

It'd also make Daniel happy; we can make es2gears produce higher numbers in swapinterval 0 mode :).

This seems like it'd need a bit of design, though; particularly - what happens on resize or other invalidation, does the client need to submit buffers in the same order as received from the server?

Also worth wondering how we can use this to make Vulkan WSI easier.