Fix the drawer curve to match Android

sky/examples/fn/widgets/drawer.dart

 part of widgets;
 
 const double _kWidth = 256.0;
 const double _kMinFlingVelocity = 0.4;
-const double _kMinAnimationDurationMS = 246.0;
-const double _kMaxAnimationDurationMS = 600.0;
+const double _kBaseSettleDurationMS = 246.0;
+const double _kMaxSettleDurationMS = 600.0;
 const Cubic _kAnimationCurve = easeOut;
 
 class DrawerAnimation {
 
   Stream<double> get onPositionChanged => _controller.stream;
 
   StreamController _controller;
   AnimationGenerator _animation;
   double _position;
   bool get _isAnimating => _animation != null;
@@ skipping 49 matching lines @@
     _animation = new AnimationGenerator(duration, begin: begin, end: end,
         curve: curve);
 
     _animation.onTick.listen(_setPosition, onDone: () {
       _animation = null;
     });
   }
 
   void _animateToPosition(double targetPosition) {
     double distance = (targetPosition - _position).abs();
-    double duration = math.max(
-        _kMinAnimationDurationMS,
-        _kMaxAnimationDurationMS * distance / _kWidth);
-
+    double targetDuration = distance / _kWidth * _kBaseSettleDurationMS;
+    double duration = math.min(targetDuration, _kMaxSettleDurationMS);
     _animate(duration, _position, targetPosition, _kAnimationCurve);
   }
 
   void handleFlingStart(event) {
     double direction = event.velocityX.sign;
     double velocityX = event.velocityX.abs() / 1000;
     if (velocityX < _kMinFlingVelocity)
       return;
 
     double targetPosition = direction < 0.0 ? -_kWidth : 0.0;
@@ skipping 101 matching lines @@
         new Container(
           key: 'Content',
           style: _contentStyle,
           inlineStyle: contentInlineStyle,
           children: children
         )
       ]
     );
   }
 }