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

sky/examples/stocks2/lib/stock_app.dart

Index: sky/examples/stocks2/lib/stock_app.dart
diff --git a/sky/examples/stocks2/lib/stock_app.dart b/sky/examples/stocks2/lib/stock_app.dart
index 8dd1fda6b9c9c90ba11a9a1cda50de9d15867fa8..fd2b2f19901c5a10ec6a392b96720d7a1b0c5f36 100644
--- a/sky/examples/stocks2/lib/stock_app.dart
+++ b/sky/examples/stocks2/lib/stock_app.dart
@@ -46,6 +46,8 @@ class StocksApp extends App {
     _drawerController = new DrawerController(_handleDrawerStatusChanged);
   }
 
+  void syncFields(StocksApp source) { }
+
   bool _isSearching = false;
   String _searchQuery;