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

sky/examples/stocks2/lib/stock_row.dart

Index: sky/examples/stocks2/lib/stock_row.dart
diff --git a/sky/examples/stocks2/lib/stock_row.dart b/sky/examples/stocks2/lib/stock_row.dart
index 4aea39c11b7b0789ef0c432cb87b3b2f58293dc9..6df131c520f8334c705ffcb64cb409a495e37867 100644
--- a/sky/examples/stocks2/lib/stock_row.dart
+++ b/sky/examples/stocks2/lib/stock_row.dart
@@ -12,13 +12,12 @@ import 'stock_arrow.dart';
 import 'stock_data.dart';
 
 class StockRow extends Component {
-  static const double kHeight = 70.0;
 
-  Stock stock;
+  StockRow({ Stock stock }) : this.stock = stock, super(key: stock.symbol);
 
-  StockRow({ Stock stock }) : super(key: stock.symbol) {
-    this.stock = stock;
-  }
+  final Stock stock;
+
+  static const double kHeight = 70.0;
 
   UINode build() {
     String lastSale = "\$${stock.lastSale.toStringAsFixed(2)}";