Code review comment for lp:~raof/mir/1hz-rendering-always

1) I think we do want to use the same MainLoop object by default, although I could see having a separate the_timer() top-level and returning the mainloop from it might make the intent clearer.

2) I deliberately didn't use a more elaborate abstraction for the initial merge, but if we want to go the whole hog, sure.

In that case, I think the policy interface wants to be something like...

class FrameDroppingPolicy
{
    virtual void swap_now_blocking(std::function<void(void)> do_frame_drop) = 0;
    virtual void swap_unblocked() = 0;
    virtual bool frame_drop_pending() const = 0; /* Possibly don't need this */
};

The SwitchingBundle would then call swap_now_blocking(...) where we currently schedule the alarm, and swap_unblocked() from compositor_release(). If we decide that calling swap_unblocked() when there isn't a swap pending is an error, then we need frame_drop_pending() otherwise we can just unconditionally call swap_unblocked().