Rectangle measure/arrange fixes.

Perspex/Shapes/Rectangle.cs

@@ -6,28 +6,13 @@
 
 namespace Perspex.Shapes
 {
-    using System;
-    using System.Reactive.Linq;
     using Perspex.Media;
 
     public class Rectangle : Shape
     {
-        private Size size;
-
         public override Geometry DefiningGeometry
         {
             get { return new RectangleGeometry(new Rect(0, 0, this.Width, this.Height)); }
         }
-
-        protected override Size MeasureOverride(Size availableSize)
-        {
-            return this.DefiningGeometry.GetRenderBounds(this.StrokeThickness).Size;
-        }
-
-        protected override Size ArrangeOverride(Size finalSize)
-        {
-            this.size = finalSize;
-            return base.ArrangeOverride(finalSize);
-        }
     }
 }

Perspex/Themes/Default/CheckBoxStyle.cs

@@ -57,22 +57,22 @@ namespace Perspex.Themes.Default
                     },
                     Children = new PerspexList<Control>
                     {
-                        new Rectangle
+                        new Border
                         {
                             Id = "checkBorder",
-                            Stroke = Brushes.Black,
-                            StrokeThickness = 2,
-                            Width = 16,
-                            Height = 16,
+                            BorderBrush = Brushes.Black,
+                            BorderThickness = 2,
+                            Width = 18,
+                            Height = 18,
                             VerticalAlignment = VerticalAlignment.Center,
                             [Grid.ColumnProperty] = 0,
                         },
-                        new Path
+                        new Rectangle
                         {
                             Id = "checkMark",
-                            Data = StreamGeometry.Parse("M0,0 L10,10 M10,0 L0,10"),
-                            Stroke = Brushes.Black,
-                            StrokeThickness = 2,
+                            Fill = Brushes.Black,
+                            Width = 10,
+                            Height = 10,
                             HorizontalAlignment = HorizontalAlignment.Center,
                             VerticalAlignment = VerticalAlignment.Center,
                             [Grid.ColumnProperty] = 0,