The sweep is Iris `97fca76`. Its two largest findings are both costs per
thing rather than per frame: a container's draw searched a list once per
child and so cost the square of its children, and a mask's rectangle was
resolved once per fragment rather than once per instance. Both now have a
rig that can see them -- `children_cost.rs` is the only one here that varies
width, and `chain_cost.rs` has a masked fixture beside its two-pixel quads.
The sweep also settles the `Fixed::div`-versus-`ratio` item this file listed,
by deleting the operation nothing performed, and adds to the pre-gate
review's waiting list the `Arc<AtomicU32>` every `StrongWidget` allocates for
a count it can never raise.