Reapply remove setInterval.

samples/swarm/swarm_ui_lib/touch/Scrollbar.dart

Index: samples/swarm/swarm_ui_lib/touch/Scrollbar.dart
diff --git a/samples/swarm/swarm_ui_lib/touch/Scrollbar.dart b/samples/swarm/swarm_ui_lib/touch/Scrollbar.dart
index de8d13c579efed4a873f3123847c2dda8902e98f..ac6a8755ab9aa2a16a13ced0af005b502dff4c4e 100644
--- a/samples/swarm/swarm_ui_lib/touch/Scrollbar.dart
+++ b/samples/swarm/swarm_ui_lib/touch/Scrollbar.dart
@@ -52,7 +52,7 @@ class Scrollbar implements ScrollListener {
   num _currentScrollStartOffset;
   bool _currentScrollVertical;
   num _currentScrollRatio;
-  num _timerId;
+  Timer _timer;
 
   bool _displayOnHover;
   bool _hovering = false;
@@ -148,7 +148,7 @@ class Scrollbar implements ScrollListener {
           // Start hiding immediately if we aren't
           // scrolling or already in the process of
           // hidng the scrollbar
-          if (!_scrollInProgress && _timerId == null) {
+          if (!_scrollInProgress && _timer == null) {
             _boundHideFn();
           }
         });
@@ -232,7 +232,8 @@ class Scrollbar implements ScrollListener {
    */
   void _onScrollerEnd(Event e) {
     _cancelTimeout();
-    _timerId = window.setTimeout(_boundHideFn, _DISPLAY_TIME);
+    _timer = new Timer(const Duration(milliseconds: _DISPLAY_TIME),
+        _boundHideFn);
     _scrollInProgress = false;
   }
   void onScrollerMoved(num scrollX, num scrollY, bool decelerating) {
@@ -281,9 +282,9 @@ class Scrollbar implements ScrollListener {
   }
 
   void _cancelTimeout() {
-    if (_timerId != null) {
-      window.clearTimeout(_timerId);
-      _timerId = null;
+    if (_timer != null) {
+      _timer.cancel();
+      _timer = null;
     }
   }