Use correct owner!

Perspex.Windows/Window.cs

@@ -23,6 +23,7 @@
             this.LayoutManager = new LayoutManager();
             this.renderer = new Renderer(this.Handle, (int)clientSize.Width, (int)clientSize.Height);
 
+            // TODO: Do this by pushing to Dispatcher rather than right away!
             this.LayoutManager.LayoutNeeded.Subscribe(x => 
             {
                 this.LayoutManager.ExecuteLayoutPass();

Perspex/Controls/TextBlock.cs

@@ -8,7 +8,7 @@
             Border.BackgroundProperty.AddOwner<TextBlock>();
 
         public static readonly PerspexProperty<Brush> ForegroundProperty =
-            PerspexProperty.Register<Border, Brush>(
+            PerspexProperty.Register<TextBlock, Brush>(
                 "Foreground",
                 defaultValue: new SolidColorBrush(0xff000000),
                 inherits: true);