Refactor settings assets proxies

Source/Editor/Content/Items/JsonAssetItem.cs

@@ -11,6 +11,8 @@ namespace FlaxEditor.Content
     /// <seealso cref="FlaxEditor.Content.AssetItem" />
     public class JsonAssetItem : AssetItem
     {
+        private readonly SpriteHandle _thumbnail;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="JsonAssetItem"/> class.
         /// </summary>
@@ -20,13 +22,27 @@ namespace FlaxEditor.Content
         public JsonAssetItem(string path, Guid id, string typeName)
         : base(path, typeName, ref id)
         {
+            _thumbnail = Editor.Instance.Icons.Document128;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="JsonAssetItem"/> class.
+        /// </summary>
+        /// <param name="path">The path.</param>
+        /// <param name="id">The identifier.</param>
+        /// <param name="typeName">Name of the resource type.</param>
+        /// <param name="thumbnail">Asset icon.</param>
+        public JsonAssetItem(string path, Guid id, string typeName, SpriteHandle thumbnail)
+        : base(path, typeName, ref id)
+        {
+            _thumbnail = thumbnail;
         }
 
         /// <inheritdoc />
         public override ContentItemSearchFilter SearchFilter => ContentItemSearchFilter.Json;
 
         /// <inheritdoc />
-        public override SpriteHandle DefaultThumbnail => Editor.Instance.Icons.Document128;
+        public override SpriteHandle DefaultThumbnail => _thumbnail;
 
         /// <inheritdoc />
         protected override bool DrawShadow => false;