Revert "[OSX] attempt to fix decoration changes when in fs mode."

This reverts commit a77e043262.

src/Avalonia.Native/WindowImpl.cs

@@ -12,10 +12,7 @@ namespace Avalonia.Native
         private readonly IAvaloniaNativeFactory _factory;
         private readonly AvaloniaNativePlatformOptions _opts;
         private readonly GlPlatformFeature _glFeature;
-        private readonly IAvnWindow _native;
-        private bool _isFullScreenActive;
-        private Interop.SystemDecorations _lastDecoration;
-
+        IAvnWindow _native;
         internal WindowImpl(IAvaloniaNativeFactory factory, AvaloniaNativePlatformOptions opts,
             GlPlatformFeature glFeature) : base(opts, glFeature)
         {
@@ -42,7 +39,7 @@ namespace Avalonia.Native
 
             bool IAvnWindowEvents.Closing()
             {
-                if (_parent.Closing != null)
+                if(_parent.Closing != null)
                 {
                     return _parent.Closing();
                 }
@@ -68,17 +65,12 @@ namespace Avalonia.Native
             _native.CanResize = value;
         }
 
-        public void SetSystemDecorations(Controls.SystemDecorations decorations)
+        public void SetSystemDecorations(Controls.SystemDecorations enabled)
         {
-            _lastDecoration = (Interop.SystemDecorations)decorations;
-
-            if (!_isFullScreenActive)
-            {
-                _native.SetHasDecorations(_lastDecoration);
-            }
+            _native.HasDecorations = (Interop.SystemDecorations)enabled;
         }
 
-        public void SetTitleBarColor(Avalonia.Media.Color color)
+        public void SetTitleBarColor (Avalonia.Media.Color color)
         {
             _native.SetTitleBarColor(new AvnColor { Alpha = color.A, Red = color.R, Green = color.G, Blue = color.B });
         }
@@ -100,17 +92,6 @@ namespace Avalonia.Native
             set
             {
                 _native.SetWindowState((AvnWindowState)value);
-
-                if (value == WindowState.FullScreen)
-                {
-                    _isFullScreenActive = true;
-                }
-                else
-                {
-                    _isFullScreenActive = false;
-
-                    _native.SetHasDecorations(_lastDecoration);
-                }
             }
         }