Set simulation tolerance field

packages/flutter/lib/src/animation/scroll_behavior.dart

@@ -108,11 +108,11 @@ Simulation _createDefaultScrollSimulation(double position, double velocity, doub
   // destiniation scroll offset.
   double endDistance = 0.5 * sky.view.devicePixelRatio;
 
-  Tolerance tolerance = new Tolerance(velocity: endVelocity, distance: endDistance);
   SpringDescription spring = new SpringDescription.withDampingRatio(mass: 1.0, springConstant: 170.0, ratio: 1.1);
-  return new ScrollSimulation(
-      position, startVelocity, minScrollOffset, maxScrollOffset, spring, _kScrollDrag, tolerance);
-
+  ScrollSimulation simulation =
+      new ScrollSimulation(position, startVelocity, minScrollOffset, maxScrollOffset, spring, _kScrollDrag)
+    ..tolerance = new Tolerance(velocity: endVelocity, distance: endDistance);
+  return simulation;
 }
 
 /// A scroll behavior that lets the user scroll beyond the scroll bounds with some resistance