Rename watchPerformance to watch

sky/sdk/lib/widgets/scrollable.dart

Index: sky/sdk/lib/widgets/scrollable.dart
diff --git a/sky/sdk/lib/widgets/scrollable.dart b/sky/sdk/lib/widgets/scrollable.dart
index 87dcbe1cd606ea89b6305054113a313888569792..807bd26a963dfc019d30154d001e211a8eb31674 100644
--- a/sky/sdk/lib/widgets/scrollable.dart
+++ b/sky/sdk/lib/widgets/scrollable.dart
@@ -30,13 +30,15 @@ abstract class Scrollable extends StatefulComponent {
     String key,
     this.backgroundColor,
     this.direction: ScrollDirection.vertical
-  }) : super(key: key) {
-    _animation = new AnimatedSimulation(_tickScrollOffset);
-  }
+  }) : super(key: key);
 
   Color backgroundColor;
   ScrollDirection direction;
 
+  void initState() {
+    _animation = new AnimatedSimulation(_tickScrollOffset);
+  }
+
   void syncFields(Scrollable source) {
     backgroundColor = source.backgroundColor;
     direction == source.direction;