Share the same arc size struct

src/Avalonia.Controls/Shapes/Rectangle.cs

@@ -63,7 +63,8 @@ namespace Avalonia.Controls.Shapes
             {
                 var rect = new Rect(Bounds.Size).Deflate(StrokeThickness / 2);
                 var geometry = new StreamGeometry();
-                double piOver2 = 1.57079633; // 90 deg to rad
+                var arcSize = new Size(x, y);
+                var piOver2 = 1.57079633; // 90 deg to rad
 
                 using (StreamGeometryContext context = geometry.Open())
                 {
@@ -89,7 +90,7 @@ namespace Avalonia.Controls.Shapes
                     context.LineTo(new Point(rect.Right - x, rect.Top));
                     context.ArcTo(
                         new Point(rect.Right, rect.Top + y),
-                        new Size(x, y),
+                        arcSize,
                         rotationAngle: piOver2,
                         isLargeArc: false,
                         SweepDirection.Clockwise);
@@ -98,7 +99,7 @@ namespace Avalonia.Controls.Shapes
                     context.LineTo(new Point(rect.Right, rect.Bottom - y));
                     context.ArcTo(
                         new Point(rect.Right - x, rect.Bottom),
-                        new Size(x, y),
+                        arcSize,
                         rotationAngle: piOver2,
                         isLargeArc: false,
                         SweepDirection.Clockwise);
@@ -107,7 +108,7 @@ namespace Avalonia.Controls.Shapes
                     context.LineTo(new Point(rect.Left + x, rect.Bottom));
                     context.ArcTo(
                         new Point(rect.Left, rect.Bottom - y),
-                        new Size(x, y),
+                        arcSize,
                         rotationAngle: piOver2,
                         isLargeArc: false,
                         SweepDirection.Clockwise);
@@ -116,7 +117,7 @@ namespace Avalonia.Controls.Shapes
                     context.LineTo(new Point(rect.Left, rect.Top + y));
                     context.ArcTo(
                         new Point(rect.Left + x, rect.Top),
-                        new Size(x, y),
+                        arcSize,
                         rotationAngle: piOver2,
                         isLargeArc: false,
                         SweepDirection.Clockwise);