Rename watchPerformance to watch

sky/sdk/lib/widgets/scrollable.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 'dart:sky' as sky;
 
 import 'package:newton/newton.dart';
 import 'package:sky/animation/animated_simulation.dart';
 import 'package:sky/animation/scroll_behavior.dart';
 import 'package:sky/theme/view_configuration.dart' as config;
@@ skipping 12 matching lines @@
 }
 
 enum ScrollDirection { vertical, horizontal }
 
 abstract class Scrollable extends StatefulComponent {
 
   Scrollable({
     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;
   }
 
   double _scrollOffset = 0.0;
   double get scrollOffset => _scrollOffset;
 
   ScrollBehavior _scrollBehavior;
   ScrollBehavior createScrollBehavior();
@@ skipping 115 matching lines @@
 
   void _handleFlingCancel(sky.GestureEvent event) {
     settleScrollOffset();
   }
 
   void _handleWheel(sky.WheelEvent event) {
     scrollBy(-event.offsetY);
   }
 
 }