Refactor fn2.dart, since it breached our 1000-line threshold.

sky/sdk/lib/framework/components2/scrollable.dart

Index: sky/sdk/lib/framework/components2/scrollable.dart
diff --git a/sky/sdk/lib/framework/components2/scrollable.dart b/sky/sdk/lib/framework/components2/scrollable.dart
deleted file mode 100644
index dee2c137335f2e4647d5b4a3700459085341f169..0000000000000000000000000000000000000000
--- a/sky/sdk/lib/framework/components2/scrollable.dart
+++ /dev/null
@@ -1,152 +0,0 @@
-// 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 '../animation/generators.dart';
-import '../animation/mechanics.dart';
-import '../animation/scroll_behavior.dart';
-import '../fn2.dart';
-import '../theme/view_configuration.dart' as config;
-import 'dart:math' as math;
-import 'dart:sky' as sky;
-
-const double _kMillisecondsPerSecond = 1000.0;
-
-double _velocityForFlingGesture(sky.GestureEvent event) {
-  return math.max(-config.kMaxFlingVelocity, math.min(config.kMaxFlingVelocity,
-      -event.velocityY)) / _kMillisecondsPerSecond;
-}
-
-abstract class ScrollClient {
-  bool ancestorScrolled(Scrollable ancestor);
-}
-
-abstract class Scrollable extends Component {
-
-  Scrollable({Object key}) : super(key: key, stateful: true);
-
-  void syncFields(Scrollable source) { }
-
-  double _scrollOffset = 0.0;
-  double get scrollOffset => _scrollOffset;
-
-  ScrollBehavior _scrollBehavior;
-  ScrollBehavior createScrollBehavior();
-  ScrollBehavior get scrollBehavior {
-    if (_scrollBehavior == null)
-      _scrollBehavior = createScrollBehavior();
-    return _scrollBehavior;
-  }
-
-  Simulation _simulation;
-
-  UINode buildContent();
-
-  UINode build() {
-    return new EventListenerNode(
-      buildContent(),
-      onPointerDown: _handlePointerDown,
-      onPointerUp: _handlePointerUpOrCancel,
-      onPointerCancel: _handlePointerUpOrCancel,
-      onGestureFlingStart: _handleFlingStart,
-      onGestureFlingCancel: _handleFlingCancel,
-      onGestureScrollUpdate: _handleScrollUpdate,
-      onWheel: _handleWheel
-    );
-  }
-
-  List<ScrollClient> _registeredScrollClients;
-
-  void registerScrollClient(ScrollClient notifiee) {
-    if (_registeredScrollClients == null)
-      _registeredScrollClients = new List<ScrollClient>();
-    setState(() {
-      _registeredScrollClients.add(notifiee);
-    });
-  }
-
-  void unregisterScrollClient(ScrollClient notifiee) {
-    if (_registeredScrollClients == null)
-      return;
-    setState(() {
-      _registeredScrollClients.remove(notifiee);
-    });
-  }
-
-  bool scrollTo(double newScrollOffset) {
-    if (newScrollOffset == _scrollOffset)
-      return false;
-    setState(() {
-      _scrollOffset = newScrollOffset;
-    });
-    if (_registeredScrollClients != null) {
-      var newList = null;
-      _registeredScrollClients.forEach((target) {
-        if (target.ancestorScrolled(this)) {
-          if (newList == null)
-            newList = new List<ScrollClient>();
-          newList.add(target);
-        }
-      });
-      setState(() {
-        _registeredScrollClients = newList;
-      });
-    }
-    return true;
-  }
-
-  bool scrollBy(double scrollDelta) {
-    var newScrollOffset = scrollBehavior.applyCurve(_scrollOffset, scrollDelta);
-    return scrollTo(newScrollOffset);
-  }
-
-  void didUnmount() {
-    _stopSimulation();
-    super.didUnmount();
-  }
-
-  void _stopSimulation() {
-    if (_simulation == null)
-      return;
-    _simulation.cancel();
-    _simulation = null;
-  }
-
-  void _startSimulation(Particle particle) {
-    _stopSimulation();
-    _simulation = scrollBehavior.release(particle);
-    if (_simulation == null)
-      return;
-    _simulation.onTick.listen((_) => scrollTo(particle.position));
-  }
-
-  Particle _createParticle([double velocity = 0.0]) {
-    return new Particle(position: _scrollOffset, velocity: velocity);
-  }
-
-  void _handlePointerDown(_) {
-    _stopSimulation();
-  }
-
-  void _handlePointerUpOrCancel(_) {
-    if (_simulation == null)
-      _startSimulation(_createParticle());
-  }
-
-  void _handleScrollUpdate(sky.GestureEvent event) {
-    scrollBy(-event.dy);
-  }
-
-  void _handleFlingStart(sky.GestureEvent event) {
-    _startSimulation(_createParticle(_velocityForFlingGesture(event)));
-  }
-
-  void _handleFlingCancel(sky.GestureEvent event) {
-    _startSimulation(_createParticle());
-  }
-
-  void _handleWheel(sky.WheelEvent event) {
-    scrollBy(-event.offsetY);
-  }
-
-}