Override default value instead of setting local value in LightDismissOverlayLayer

src/Avalonia.Controls/Primitives/LightDismissOverlayLayer.cs

@@ -2,6 +2,7 @@ using System;
 using System.Linq;
 using Avalonia.Controls.Templates;
 using Avalonia.Input;
+using Avalonia.Media;
 using Avalonia.Rendering;
 using Avalonia.Styling;
 using Avalonia.VisualTree;
@@ -17,6 +18,11 @@ namespace Avalonia.Controls.Primitives
     {
         public IInputElement? InputPassThroughElement { get; set; }
 
+        static LightDismissOverlayLayer()
+        {
+            BackgroundProperty.OverrideDefaultValue<LightDismissOverlayLayer>(Brushes.Transparent);
+        }
+
         /// <summary>
         /// Returns the light dismiss overlay for a specified visual.
         /// </summary>

src/Avalonia.Controls/Primitives/VisualLayerManager.cs

@@ -74,7 +74,6 @@ namespace Avalonia.Controls.Primitives
                 {
                     rv = new LightDismissOverlayLayer
                     {
-                        Background = Brushes.Transparent,
                         IsVisible = false
                     };