Code review comment for lp:~afrantzis/mir/consume-only-not-rendered-buffers

> + virtual std::chrono::steady_clock::time_point time_last_buffer_acquired()
> const = 0;
>
> this makes Renderable leak the buffer stream abstraction even worse than it
> has before (I expound on this in my mp review:
> https://code.launchpad.net/~kdub/mir/produce-renderlist-for-particular-
> compositor/+merge/215052/comments/514979)

Note that the "buffer_acquired" in time_last_buffer_acquired() doesn't refer to the underlying buffer stream, but to Renderable::buffer(). That is, it returns the time point when someone last called Renderable::buffer(), regardless of the underlying implementation.