Add TextStyle fontFamily:, extend support for fontWeight:

sky/examples/rendering/interactive_flex.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';
 import 'dart:math' as math;
 import 'package:sky/framework/net/image_cache.dart' as image_cache;
 import 'package:sky/app/view.dart';
+import 'package:sky/painting/text_style.dart';
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/block.dart';
 import 'package:sky/rendering/flex.dart';
 import 'package:sky/rendering/object.dart';
 import 'package:sky/rendering/paragraph.dart';
 import '../lib/solid_color_box.dart';
 
 class Touch {
   final double x;
   final double y;
@@ skipping 71 matching lines @@
   column.parentData.flex = 8;
 
   RenderDecoratedBox root = new RenderDecoratedBox(
     decoration: new BoxDecoration(backgroundColor: const Color(0xFFFFFFFF)),
     child: row
   );
 
   app = new AppView(root: root);
   view.setEventCallback(handleEvent);
 }