iris: drive animation from painter frame time

core/src/widget/mod.rs

@@ -47,11 +47,6 @@ pub trait Widget: Any {
     fn child_order(&self) -> ChildOrder {
         ChildOrder::Draw
     }
-
-    #[allow(unused_variables)]
-    fn tick(&mut self, now: std::time::Instant) -> bool {
-        false
-    }
 }
 
 impl Widget for () {