[Effen] Add AnimatedComponent base class

sky/framework/components/scrollable.dart

Index: sky/framework/components/scrollable.dart
diff --git a/sky/framework/components/scrollable.dart b/sky/framework/components/scrollable.dart
index 9d4fc6a79dd64f0de19f97fa2bea30d50f2fa867..5590bf9e0e7a09da9f8454c8041e50e70d7c6047 100644
--- a/sky/framework/components/scrollable.dart
+++ b/sky/framework/components/scrollable.dart
@@ -24,7 +24,9 @@ abstract class Scrollable extends Component {
   double _scrollOffset = 0.0;
   Simulation _simulation;
 
-  Scrollable({Object key, this.scrollBehavior}) : super(key: key);
+  Scrollable({Object key, this.scrollBehavior}) : super(key: key) {
+    onDidUnmount(_stopSimulation);
+  }
 
   Node buildContent();
 
@@ -41,11 +43,6 @@ abstract class Scrollable extends Component {
     );
   }
 
-  void didUnmount() {
-    super.didUnmount();
-    _stopSimulation();
-  }
-
   bool scrollBy(double scrollDelta) {
     var newScrollOffset = scrollBehavior.applyCurve(_scrollOffset, scrollDelta);
     if (newScrollOffset == _scrollOffset)