Fix drag point for application icons

We need to return the "thing that is being dragged" from
getDragActorSource() so that dnd.js can figure out the right
relationship between the dragged object and cursor.

https://bugzilla.gnome.org/show_bug.cgi?id=607351

js/ui/appDisplay.js

@@ -504,10 +504,10 @@ AppWellIcon.prototype = {
         return this.app.create_icon_texture(APPICON_SIZE);
     },
 
-    // Returns the original icon that is being used as a source for the cloned texture
-    // that represents the item as it is being dragged.
+    // Returns the original actor that should align with the actor
+    // we show as the item is being dragged.
     getDragActorSource: function() {
-        return this.actor;
+        return this._icon.icon;
     }
 }
 Signals.addSignalMethods(AppWellIcon.prototype);