Make stocks-fn match the style for the Sky SDK

sky/examples/stocks-fn/lib/stock_arrow.dart

-part of stocksapp;
+// 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:math';
+import 'package:sky/framework/fn.dart';
 
 class StockArrow extends Component {
-
-  double percentChange;
-
-  static Style _style = new Style('''
+  static final Style _style = new Style('''
     width: 40px;
     height: 40px;
     display: flex;
     align-items: center;
     justify-content: center;
     border-radius: 40px;
     margin-right: 16px;
     border: 1px solid transparent;'''
   );
 
-  static Style _upStyle = new Style('''
+  static final Style _upStyle = new Style('''
     width: 0;
     height: 0;
     border-left: 9px solid transparent;
     border-right: 9px solid transparent;
     margin-bottom: 3px;
     border-bottom: 9px solid white;'''
   );
 
-  static Style _downStyle = new Style('''
+  static final Style _downStyle = new Style('''
     width: 0;
     height: 0;
     border-left: 9px solid transparent;
     border-right: 9px solid transparent;
     margin-top: 3px;
     border-top: 9px solid white'''
   );
 
+  double percentChange;
+
   StockArrow({ Object key, this.percentChange }) : super(key: key);
 
+  // TODO(abarth): These should use sky/framework/theme/colors.dart.
   final List<String> _kRedColors = [
     '#E57373',
     '#EF5350',
     '#F44336',
     '#E53935',
     '#D32F2F',
     '#C62828',
     '#B71C1C',
   ];
 
+  // TODO(abarth): These should use sky/framework/theme/colors.dart.
   final List<String> _kGreenColors = [
     '#81C784',
     '#66BB6A',
     '#4CAF50',
     '#43A047',
     '#388E3C',
     '#2E7D32',
     '#1B5E20',
   ];
 
@@ skipping 19 matching lines @@
       style: _style,
       children: [
         new Container(
           inlineStyle: 'border-$type-color: $border',
           style: up ? _upStyle : _downStyle
         )
       ]
     );
   }
 }