[Layout] Put in some guards to prevent us from reintroducing 'display' properties into the CSS.

sky/examples/stocks/lib/stock_arrow.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:math';
 import 'package:sky/framework/fn.dart';
+import 'package:sky/framework/layout.dart';
 
 class StockArrow extends Component {
   static final Style _style = new Style('''
     width: 40px;
     height: 40px;
-    display: flex;
-    flex-direction: row;
     align-items: center;
     justify-content: center;
     border-radius: 40px;
     margin-right: 16px;
     border: 1px solid transparent;'''
   );
 
   static final Style _upStyle = new Style('''
     width: 0;
     height: 0;
@@ skipping 48 matching lines @@
     if (percentChange > 0)
       return _kGreenColors[_colorIndexForPercentChange(percentChange)];
     return _kRedColors[_colorIndexForPercentChange(percentChange)];
   }
 
   UINode build() {
     String border = _colorForPercentChange(percentChange).toString();
     bool up = percentChange > 0;
     String type = up ? 'bottom' : 'top';
 
-    return new Container(
+    return new FlexContainer(
       inlineStyle: 'border-color: $border',
+      direction: FlexDirection.Row,
       style: _style,
       children: [
         new Container(
           inlineStyle: 'border-$type-color: $border',
           style: up ? _upStyle : _downStyle
         )
       ]
     );
   }
 }