Some trivial animation library cleanup.

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

@@ -48,7 +48,7 @@ class AnimationController extends Animation<double>
   /// * debugLabel is a string to help identify this animation during debugging (used by toString).
   ///
   /// This constructor is most useful for animations that will be driven using a
-  /// physics simulation, especially when the physics simulation as no
+  /// physics simulation, especially when the physics simulation has no
   /// pre-determined bounds.
   AnimationController.unbounded({
     double value: 0.0,
@@ -128,48 +128,6 @@ class AnimationController extends Animation<double>
     return animateTo(_direction == AnimationDirection.forward ? upperBound : lowerBound);
   }
 
-  /// Stops running this animation.
-  void stop() {
-    _simulation = null;
-    _ticker.stop();
-  }
-
-  /// Stops running this animation.
-  void dispose() {
-    stop();
-  }
-
-  /// Flings the timeline with an optional force (defaults to a critically
-  /// damped spring) and initial velocity. If velocity is positive, the
-  /// animation will complete, otherwise it will dismiss.
-  Future fling({ double velocity: 1.0, Force force }) {
-    force ??= kDefaultSpringForce;
-    _direction = velocity < 0.0 ? AnimationDirection.reverse : AnimationDirection.forward;
-    return animateWith(force.release(value, velocity));
-  }
-
-  /// Starts running this animation in the forward direction, and
-  /// restarts the animation when it completes.
-  Future repeat({ double min: 0.0, double max: 1.0, Duration period }) {
-    period ??= duration;
-    return animateWith(new _RepeatingSimulation(min, max, period));
-  }
-
-  /// Drives the animation according to the given simulation.
-  Future animateWith(Simulation simulation) {
-    stop();
-    return _startSimulation(simulation);
-  }
-
-  AnimationStatus _lastStatus = AnimationStatus.dismissed;
-  void _checkStatusChanged() {
-    AnimationStatus newStatus = status;
-    AnimationStatus oldStatus = _lastStatus;
-    _lastStatus = newStatus;
-    if (oldStatus != newStatus)
-      notifyStatusListeners(newStatus);
-  }
-
   /// Drives the animation from its current value to target.
   Future animateTo(double target, { Duration duration, Curve curve: Curves.linear }) {
     Duration simulationDuration = duration;
@@ -190,6 +148,28 @@ class AnimationController extends Animation<double>
     return _startSimulation(new _TweenSimulation(_value, target, simulationDuration, curve));
   }
 
+  /// Starts running this animation in the forward direction, and
+  /// restarts the animation when it completes.
+  Future repeat({ double min: 0.0, double max: 1.0, Duration period }) {
+    period ??= duration;
+    return animateWith(new _RepeatingSimulation(min, max, period));
+  }
+
+  /// Flings the timeline with an optional force (defaults to a critically
+  /// damped spring) and initial velocity. If velocity is positive, the
+  /// animation will complete, otherwise it will dismiss.
+  Future fling({ double velocity: 1.0, Force force }) {
+    force ??= kDefaultSpringForce;
+    _direction = velocity < 0.0 ? AnimationDirection.reverse : AnimationDirection.forward;
+    return animateWith(force.release(value, velocity));
+  }
+
+  /// Drives the animation according to the given simulation.
+  Future animateWith(Simulation simulation) {
+    stop();
+    return _startSimulation(simulation);
+  }
+
   Future _startSimulation(Simulation simulation) {
     assert(simulation != null);
     assert(!isAnimating);
@@ -198,6 +178,26 @@ class AnimationController extends Animation<double>
     return _ticker.start();
   }
 
+  /// Stops running this animation.
+  void stop() {
+    _simulation = null;
+    _ticker.stop();
+  }
+
+  /// Stops running this animation.
+  void dispose() {
+    stop();
+  }
+
+  AnimationStatus _lastStatus = AnimationStatus.dismissed;
+  void _checkStatusChanged() {
+    AnimationStatus newStatus = status;
+    AnimationStatus oldStatus = _lastStatus;
+    _lastStatus = newStatus;
+    if (oldStatus != newStatus)
+      notifyStatusListeners(newStatus);
+  }
+
   void _tick(Duration elapsed) {
     double elapsedInSeconds = elapsed.inMicroseconds.toDouble() / Duration.MICROSECONDS_PER_SECOND;
     _value = _simulation.x(elapsedInSeconds);

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

@@ -47,10 +47,10 @@ class _AlwaysDismissedAnimation extends Animation<double> {
 const Animation<double> kAlwaysDismissedAnimation = const _AlwaysDismissedAnimation();
 
 /// An animation that is always stopped at a given value.
-class AlwaysStoppedAnimation extends Animation<double> {
+class AlwaysStoppedAnimation<T> extends Animation<T> {
   const AlwaysStoppedAnimation(this.value);
 
-  final double value;
+  final T value;
 
   void addListener(VoidCallback listener) { }
   void removeListener(VoidCallback listener) { }

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

@@ -47,7 +47,7 @@ class _ChainedEvaluation<T> extends Animatable<T> {
 
   T evaluate(Animation<double> animation) {
     double value = _parent.evaluate(animation);
-    return _evaluatable.evaluate(new AlwaysStoppedAnimation(value));
+    return _evaluatable.evaluate(new AlwaysStoppedAnimation<double>(value));
   }
 }