iris: drive animation from painter frame time

scripts/rigs/ui-profile/tests/frame_profile.rs

@@ -31,8 +31,6 @@ fn what_a_fling_frame_costs() {
         let velocity = if pass % 2 == 0 { VELOCITY } else { -VELOCITY };
         let list = (opened.screen.list)(&mut h.rsc);
         list.fling(velocity);
-        let id = opened.screen.list.id();
-        h.rsc.ui.animate(id);
 
         let mut frames = Vec::new();
         let mut layouts = Vec::new();