ADD Added missing XML documentation.

NTFY-16


git-svn-id: https://svn.evolvesoftware.ch/repos/evolve.net/WPF/NotifyIcon@211 9f600761-6f11-4665-b6dc-0185e9171623

Source/NotifyIconWpf/TaskbarIcon.Declarations.cs

@@ -142,6 +142,9 @@ namespace Hardcodet.Wpf.TaskbarNotification
             = DependencyProperty.RegisterReadOnly("CustomBalloon", typeof (Popup), typeof (TaskbarIcon),
                 new FrameworkPropertyMetadata(null));
 
+        /// <summary>
+        /// Maintains a currently displayed custom balloon.
+        /// </summary>
         public static readonly DependencyProperty CustomBalloonProperty
             = CustomBalloonPropertyKey.DependencyProperty;