Make the 'XwtComponent.Tag' Property virtual so that it can be overri…

…den by a control which in turn makes it possible to set the tag property on the native control itself.

Xwt.WPF/Xwt.WPFBackend/WindowFrameBackend.cs

@@ -59,6 +59,7 @@ void IWindowFrameBackend.Initialize (IWindowFrameEventSink eventSink)
 			Initialize ();
 		}
 
+		public object Tag { get { return window.Tag; } set { window.Tag = value; } }
 		public ApplicationContext Context { get; private set; }
 
 		public virtual void Initialize ()

Xwt/Xwt.Backends/IWindowFrameBackend.cs

@@ -92,6 +92,8 @@ public interface IWindowFrameBackend: IBackend
 		/// </summary>
 		/// <value>The screen.</value>
 		object Screen { get; }
+
+		object Tag { get; set; }
 	}
 
 	public interface IWindowFrameEventSink

Xwt/Xwt/WindowFrame.cs

@@ -72,7 +72,7 @@ public class WindowFrame: XwtComponent, IAnimatable
 		bool pendingReallocation;
 		Image icon;
 		WindowFrame transientFor;
-
+		public override object Tag { get { return Backend.Tag; } set { Backend.Tag = value; } }
 		protected class WindowBackendHost: BackendHost<WindowFrame,IWindowFrameBackend>, IWindowFrameEventSink
 		{
 			protected override void OnBackendCreated ()
@@ -83,7 +83,9 @@ protected override void OnBackendCreated ()
 				Parent.size = Backend.Bounds.Size;
 				Backend.EnableEvent (WindowFrameEvent.BoundsChanged);
 			}
+
 
+
 			public void OnBoundsChanged (Rectangle bounds)
 			{
 				Parent.OnBoundsChanged (new BoundsChangedEventArgs () { Bounds = bounds });

Xwt/Xwt/XwtComponent.cs

@@ -76,7 +76,7 @@ protected virtual BackendHost CreateBackendHost ()
 		/// <summary>
 		/// A value, that can be used to identify this component
 		/// </summary>
-		public object Tag { get; set; }
+		public virtual object Tag { get; set; }
 
 		/// <summary>
 		/// Maps an event handler of an Xwt component to an event identifier.