Restore stock_arrow elemnt of the stocks2 demo

sky/examples/stocks2/lib/stock_row.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: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 {
   static const double kHeight = 100.0;
 
   Stock stock;
 
   StockRow({ Stock stock }) : super(key: stock.symbol) {
     this.stock = stock;
   }
 
   UINode build() {
     String lastSale = "\$${stock.lastSale.toStringAsFixed(2)}";
 
     String changeInPrice = "${stock.percentChange.toStringAsFixed(2)}%";
     if (stock.percentChange > 0)
       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,
         padding: const EdgeDims.only(right: 16.0),
         // text-align: right
         child: new Text(lastSale)
       ),
       // text-align: right, ${typography.black.caption};
       new SizedBox(
         width: 75.0,
         child: new Text(changeInPrice)
       ),
     ];
 
     return new Container(
       padding: const EdgeDims(16.0, 16.0, 20.0, 16.0),
       height: kHeight,
       decoration: const BoxDecoration(
         backgroundColor: const sky.Color(0xFFFFFFFF),
         border: const Border(
           bottom: const BorderSide(
             color: const sky.Color(0xFFF4F4F4),
             width: 1.0))),
       child: new FlexContainer(children: children));
   }
 }