Switch scroll physics over to using newton

sky/sdk/lib/widgets/scrollable.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:sky' as sky;
 
-import '../animation/generators.dart';
-import '../animation/mechanics.dart';
+import 'package:newton/newton.dart';
+
+import '../animation/animated_simulation.dart';
 import '../animation/scroll_behavior.dart';
 import '../theme/view_configuration.dart' as config;
 import 'basic.dart';
 import 'material.dart';
 
 const double _kMillisecondsPerSecond = 1000.0;
 
 double _velocityForFlingGesture(double eventVelocity) {
   return eventVelocity.clamp(-config.kMaxFlingVelocity, config.kMaxFlingVelocity) /
     _kMillisecondsPerSecond;
 }
 
 abstract class ScrollClient {
   bool ancestorScrolled(Scrollable ancestor);
 }
 
 enum ScrollDirection { vertical, horizontal }
 
 abstract class Scrollable extends StatefulComponent {
 
   Scrollable({
     String key,
     this.backgroundColor,
     this.direction: ScrollDirection.vertical
-  }) : super(key: key);
+  }) : super(key: key) {
+    _animation = new AnimatedSimulation(_tickScrollOffset);
+  }
 
   Color backgroundColor;
   ScrollDirection direction;
 
   void syncFields(Scrollable source) {
     backgroundColor = source.backgroundColor;
     direction == source.direction;
   }
 
   double _scrollOffset = 0.0;
   double get scrollOffset => _scrollOffset;
 
   ScrollBehavior _scrollBehavior;
   ScrollBehavior createScrollBehavior();
   ScrollBehavior get scrollBehavior {
     if (_scrollBehavior == null)
       _scrollBehavior = createScrollBehavior();
     return _scrollBehavior;
   }
 
-  Simulation _simulation;
+  AnimatedSimulation _animation;
 
   Widget buildContent();
 
   Widget build() {
     return new Listener(
       child: new Material(
         type: MaterialType.canvas,
         child: buildContent(),
         color: backgroundColor
       ),
@@ skipping 51 matching lines @@
     var newScrollOffset = scrollBehavior.applyCurve(_scrollOffset, scrollDelta);
     return scrollTo(newScrollOffset);
   }
 
   void didUnmount() {
     _stopSimulation();
     super.didUnmount();
   }
 
   void settleScrollOffset() {
-    _startSimulation(_createParticle());
+    _startSimulation();
   }
 
   void _stopSimulation() {
-    if (_simulation == null)
-      return;
-    _simulation.cancel();
-    _simulation = null;
+    _animation.stop();
   }
 
-  void _startSimulation(Particle particle) {
+  void _startSimulation({ double velocity: 0.0 }) {
     _stopSimulation();
-    _simulation = scrollBehavior.release(particle);
-    if (_simulation == null)
-      return;
-    _simulation.onTick.listen((_) => scrollTo(particle.position));
+    print("velocity=$velocity");
+    Simulation simulation = scrollBehavior.release(scrollOffset, velocity);
+    if (simulation != null)
+      _animation.start(simulation);
   }
 
-  Particle _createParticle([double velocity = 0.0]) {
-    return new Particle(position: _scrollOffset, velocity: velocity);
+  void _tickScrollOffset(double value) {
+    scrollTo(value);
   }
 
   void _handlePointerDown(_) {
     _stopSimulation();
   }
 
   void _handlePointerUpOrCancel(_) {
-    if (_simulation == null)
+    if (!_animation.isAnimating)
       settleScrollOffset();
   }
 
   void _handleScrollUpdate(sky.GestureEvent event) {
     scrollBy(direction == ScrollDirection.horizontal ? event.dx : -event.dy);
   }
 
   void _handleFlingStart(sky.GestureEvent event) {
     double eventVelocity = direction == ScrollDirection.horizontal
       ? -event.velocityX
       : -event.velocityY;
-    _startSimulation(_createParticle(_velocityForFlingGesture(eventVelocity)));
+    _startSimulation(velocity: _velocityForFlingGesture(eventVelocity));
   }
 
   void _handleFlingCancel(sky.GestureEvent event) {
     settleScrollOffset();
   }
 
   void _handleWheel(sky.WheelEvent event) {
     scrollBy(-event.offsetY);
   }
 
 }