Enable antialiasing on Paint by default.

sky/sdk/lib/framework/components2/checkbox.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 'package:sky/framework/theme2/colors.dart' as colors;
 
 import 'dart:sky' as sky;
 import '../fn2.dart';
 import '../rendering/box.dart';
 import '../rendering/object.dart';
@@ skipping 25 matching lines @@
     const double edgeRadius = 1.0;
     return new EventListenerNode(
       new Container(
         margin: const EdgeDims.symmetric(horizontal: 5.0),
         width: edgeSize + 2.0,
         height: edgeSize + 2.0,
         child: new CustomPaint(
           callback: (sky.Canvas canvas) {
 
             sky.Paint paint = new sky.Paint()..color = color
-                                             ..isAntiAlias = true
                                              ..strokeWidth = 2.0;
 
             // Draw the outer rrect
             paint.setStyle(checked ? sky.PaintingStyle.strokeAndFill : sky.PaintingStyle.stroke);
             sky.Rect rect = new sky.Rect.fromLTRB(0.0, 0.0, edgeSize, edgeSize);
             sky.RRect rrect = new sky.RRect()..setRectXY(rect, edgeRadius, edgeRadius);
             canvas.drawRRect(rrect, paint);
 
             // Draw the inner check
             if (checked) {
               // TODO(jackson): Use the theme color
               paint.color = const sky.Color(0xFFFFFFFF);
               paint.setStyle(sky.PaintingStyle.stroke);
               sky.Path path = new sky.Path();
               path.moveTo(edgeSize * 0.2, edgeSize * 0.5);
               path.lineTo(edgeSize * 0.4, edgeSize * 0.7);
               path.lineTo(edgeSize * 0.8, edgeSize * 0.3);
               canvas.drawPath(path, paint);
             }
           }
         )
       ),
       onGestureTap: _handleClick
     );
   }
 
 }