Remove source icon when a corresponding window is activated

Source icons are no longer needed to inform the user about events
having occured in a particular application when (s)he activates the
window - treat that case just as if the user had clicked the source
icon.

https://bugzilla.gnome.org/show_bug.cgi?id=610494

js/ui/notificationDaemon.js

@@ -100,6 +100,9 @@ NotificationDaemon.prototype = {
                                   Lang.bind(this, this._lostName));
 
         this._currentNotifications = {};
+
+        Shell.WindowTracker.get_default().connect('notify::focus-app',
+            Lang.bind(this, this._onFocusAppChanged));
     },
 
     _acquiredName: function() {
@@ -260,6 +263,10 @@ NotificationDaemon.prototype = {
         ];
     },
 
+    _onFocusAppChanged: function(tracker) {
+        Main.messageTray.removeSourceByApp(tracker.focus_app);
+    },
+
     _actionInvoked: function(notification, action, source, id) {
         this._emitActionInvoked(id, action);
         source.destroy();