Standardize Default member in PixelRect

samples/ControlCatalog/Pages/ImagePage.xaml.cs

@@ -70,7 +70,7 @@ namespace ControlCatalog.Pages
                 3 => new PixelRect(new PixelPoint(bitmapWidth - cropSize.Width, 0), cropSize),
                 4 => new PixelRect(new PixelPoint(0, bitmapHeight - cropSize.Height), cropSize),
                 5 => new PixelRect(new PixelPoint(bitmapWidth - cropSize.Width, bitmapHeight - cropSize.Height), cropSize),
-                _ => PixelRect.Empty
+                _ => PixelRect.Default
             };
             
         }

src/Avalonia.Base/PixelRect.cs

@@ -10,9 +10,13 @@ namespace Avalonia
     public readonly struct PixelRect : IEquatable<PixelRect>
     {
         /// <summary>
-        /// An empty rectangle.
+        /// A shared default instance representing an empty rectangle.
         /// </summary>
-        public static readonly PixelRect Empty = default;
+        public static readonly PixelRect Default = default;
+
+        /// <inheritdoc cref="Default"/>
+        [Obsolete("Use Default instead.")]
+        public static readonly PixelRect Empty = Default;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="PixelRect"/> structure.
@@ -261,7 +265,7 @@ namespace Avalonia
             }
             else
             {
-                return Empty;
+                return Default;
             }
         }