perf: Remove use of generic delegate in Brush.AssignAndObserveBrush

Author: jeromelaban

src/Uno.UI/UI/Xaml/Media/Brush.Android.cs

@@ -16,6 +16,8 @@ namespace Windows.UI.Xaml.Media
 	//Android partial for Brush
 	public partial class Brush
 	{
+		internal delegate void ColorSetterHandler(Android.Graphics.Color color);
+
 		/// <summary>
 		/// Return a paint with Fill style
 		/// </summary>
@@ -42,7 +44,7 @@ internal Paint GetStrokePaint(Windows.Foundation.Rect destinationRect)
 
 		protected virtual Paint GetPaintInner(Rect destinationRect) => throw new InvalidOperationException();
 
-		internal static IDisposable AssignAndObserveBrush(Brush b, Action<Android.Graphics.Color> colorSetter, Action imageBrushCallback = null)
+		internal static IDisposable AssignAndObserveBrush(Brush b, ColorSetterHandler colorSetter, Action imageBrushCallback = null)
 		{
 			if (b is SolidColorBrush colorBrush)
 			{

src/Uno.UI/UI/Xaml/Media/Brush.Skia.cs

@@ -9,7 +9,9 @@ namespace Windows.UI.Xaml.Media
 {
 	public abstract partial class Brush
 	{
-		internal static IDisposable AssignAndObserveBrush(Brush b, Action<Color> colorSetter, Action imageBrushCallback = null)
+		internal delegate void ColorSetterHandler(Color color);
+
+		internal static IDisposable AssignAndObserveBrush(Brush b, ColorSetterHandler colorSetter, Action imageBrushCallback = null)
 		{
 			var disposables = new CompositeDisposable();
 

src/Uno.UI/UI/Xaml/Media/Brush.iOSmacOS.cs

@@ -19,7 +19,9 @@ namespace Windows.UI.Xaml.Media
 	// iOS partial for SolidColorBrush
 	public partial class Brush
 	{
-		internal static IDisposable AssignAndObserveBrush(Brush b, Action<CGColor> colorSetter, Action imageBrushCallback = null)
+		internal delegate void ColorSetterHandler(CGColor color);
+
+		internal static IDisposable AssignAndObserveBrush(Brush b, ColorSetterHandler colorSetter, Action imageBrushCallback = null)
 		{
 			if (b is SolidColorBrush colorBrush)
 			{

src/Uno.UI/UI/Xaml/Media/Brush.wasm.cs

@@ -3,12 +3,21 @@
 using System.Text;
 using Uno.Extensions;
 using Uno.Disposables;
+using Windows.UI; // Required for WinUI 3+ Color
 
 namespace Windows.UI.Xaml.Media
 {
 	public abstract partial class Brush
 	{
-		internal static IDisposable AssignAndObserveBrush(Brush b, Action<Windows.UI.Color> colorSetter, Action imageBrushCallback = null)
+		/// <summary>
+		/// Color action handler
+		/// </summary>
+		/// <remarks>
+		/// This delegate is not an <see cref="Action{T}"/> to account for https://github.com/dotnet/runtime/issues/50757
+		/// </remarks>
+		internal delegate void ColorSetterHandler(Color color);
+
+		internal static IDisposable AssignAndObserveBrush(Brush b, ColorSetterHandler colorSetter, Action imageBrushCallback = null)
 		{
 			if (b is SolidColorBrush colorBrush)
 			{