iris: drive animation from painter frame time

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

@@ -138,8 +138,6 @@ fn what_a_fling_uploads() {
     for pass in 0..PASSES {
         let velocity = if pass % 2 == 0 { VELOCITY } else { -VELOCITY };
         (opened.screen.list)(&mut h.rsc).fling(velocity);
-        let id = opened.screen.list.id();
-        h.rsc.ui.animate(id);
         let end = t + PASS_CAP_MS;
         while t <= end {
             t += PHONE_FRAME_MS;