Restore stock_arrow elemnt of the stocks2 demo

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 4990a55033226095f5111c28fe4864deaedd285b..913ff9cc980efd898c80376636c28e040425efa2 100644
--- a/sky/examples/stocks2/lib/stock_row.dart
+++ b/sky/examples/stocks2/lib/stock_row.dart
@@ -7,7 +7,7 @@ import 'package:sky/framework/components2/ink_well.dart';
 import 'package:sky/framework/fn2.dart';
 import 'package:sky/framework/rendering/box.dart';
 import 'package:sky/framework/theme/typography.dart' as typography;
-// import 'stock_arrow.dart';
+import 'stock_arrow.dart';
 import 'stock_data.dart';
 
 class StockRow extends Component {
@@ -27,9 +27,9 @@ class StockRow extends Component {
       changeInPrice = "+" + changeInPrice;
 
     List<UINode> children = [
-      // new StockArrow(
-      //   percentChange: stock.percentChange
-      // ),
+      new StockArrow(
+        percentChange: stock.percentChange
+      ),
       new FlexExpandingChild(new Text(stock.symbol)),
       new Container(
         width: 75.0,