Fix the floating action button.

sky/sdk/lib/painting/box_painter.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' as math;
 import 'dart:sky' as sky;
 import 'dart:sky' show Point, Offset, Size, Rect, Color, Paint, Path;
 
 import 'shadows.dart';
 
@@ skipping 189 matching lines @@
     return _cachedBackgroundPaint;
   }
 
   void paint(sky.Canvas canvas, Rect rect) {
     if (_decoration.backgroundColor != null || _decoration.boxShadow != null ||
         _decoration.gradient != null) {
       switch (_decoration.shape) {
         case Shape.circle:
           assert(_decoration.borderRadius == null);
           Point center = rect.center;
-          Size size = rect.size;
-          double radius = math.min(size.width, size.height) / 2.0;
+          double radius = rect.shortestSide / 2.0;
           canvas.drawCircle(center, radius, _backgroundPaint);
           break;
         case Shape.rectangle:
           if (_decoration.borderRadius == null)
             canvas.drawRect(rect, _backgroundPaint);
           else
             canvas.drawRRect(new sky.RRect()..setRectXY(rect, _decoration.borderRadius, _decoration.borderRadius), _backgroundPaint);
           break;
       }
     }
@@ skipping 41 matching lines @@
       path = new Path();
       path.moveTo(rect.left, rect.bottom);
       path.lineTo(rect.left + _decoration.border.left.width, rect.bottom - _decoration.border.bottom.width);
       path.lineTo(rect.left + _decoration.border.left.width, rect.top + _decoration.border.top.width);
       path.lineTo(rect.left, rect.top);
       path.close();
       canvas.drawPath(path, paint);
     }
   }
 }