Combine window.setTimeout/setInterval with Timer and Timer.repeating. Also

samples/swarm/swarm_ui_lib/view/SliderMenu.dart

Index: samples/swarm/swarm_ui_lib/view/SliderMenu.dart
diff --git a/samples/swarm/swarm_ui_lib/view/SliderMenu.dart b/samples/swarm/swarm_ui_lib/view/SliderMenu.dart
index 3eae27ed91bb466f1f9ea2a555ad3c91665cf106..e3b955f77715007af1ecdc99bac213c17e79001f 100644
--- a/samples/swarm/swarm_ui_lib/view/SliderMenu.dart
+++ b/samples/swarm/swarm_ui_lib/view/SliderMenu.dart
@@ -157,7 +157,7 @@ class SliderMenu extends View {
   void updateIndicator(bool animate) {
     if (selectedItem != null) {
       // calculate where we want to put the triangle
-      window.setImmediate(() {
+      window.immediate.then((_) {
         num x = selectedItem.offsetLeft +
             selectedItem.offsetWidth / 2 - TRIANGLE_WIDTH / 2;
         _moveIndicator(x, animate);