Added missing clamped_simulation.dart file

packages/flutter/lib/animation.dart

@@ -10,6 +10,7 @@ library animation;
 export 'src/animation/animated_simulation.dart';
 export 'src/animation/animated_value.dart';
 export 'src/animation/animation_performance.dart';
+export 'src/animation/clamped_simulation.dart';
 export 'src/animation/curves.dart';
 export 'src/animation/forces.dart';
 export 'src/animation/scheduler.dart';

packages/flutter/lib/src/animation/clamped_simulation.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 'package:newton/newton.dart';
+
+class ClampedSimulation extends Simulation {
+  ClampedSimulation(this.simulation, {
+    this.xMin: double.NEGATIVE_INFINITY,
+    this.xMax: double.INFINITY,
+    this.dxMin: double.NEGATIVE_INFINITY,
+    this.dxMax: double.INFINITY
+  }) {
+    assert(simulation != null);
+    assert(xMax >= xMin);
+    assert(dxMax >= dxMin);
+  }
+
+  final Simulation simulation;
+  final double xMin;
+  final double xMax;
+  final double dxMin;
+  final double dxMax;
+
+  double x(double time) => simulation.x(time).clamp(xMin, xMax);
+  double dx(double time) => simulation.dx(time).clamp(dxMin, dxMax);
+  bool isDone(double time) => simulation.isDone(time);
+}