Remove one more use of mirrors: Components now have to explicitly sync their fields.

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
index bc76e4026345c1523dff20eeb3ea371b604d7bdc..b43583325d934573a60ccf0bc7425b7125fae87c 100644
--- a/sky/sdk/lib/framework/components2/scrollable.dart
+++ b/sky/sdk/lib/framework/components2/scrollable.dart
@@ -23,10 +23,12 @@ abstract class ScrollClient {
 
 abstract class Scrollable extends Component {
 
-  Scrollable({Object key}) : super(key: key) {
+  Scrollable({Object key}) : super(key: key, stateful: true) {
     onDidUnmount(_stopSimulation);
   }
 
+  void syncFields(Scrollable source) { }
+
   double _scrollOffset = 0.0;
   double get scrollOffset => _scrollOffset;