Add eventListeners usage example in APIdoc

lib/OpenLayers/Tile.js

@@ -44,6 +44,21 @@ OpenLayers.Tile = OpenLayers.Class({
      *     object will be registered with <OpenLayers.Events.on>.  Object
      *     structure must be a listeners object as shown in the example for
      *     the events.on method.
+     *
+     * This options can be set in the ``tileOptions`` option from
+     * <OpenLayers.Layer.Grid>. For example, to be notified of the
+     * ``loadend`` event of each tiles:
+     * (code)
+     * new OpenLayers.Layer.OSM('osm', 'http://tile.openstreetmap.org/${z}/${x}/${y}.png', {
+     *     tileOptions: {
+     *         eventListeners: {
+     *             'loadend': function(evt) {
+     *                 // do something on loadend
+     *             }
+     *         }
+     *     }
+     * });
+     * (end)
      */
     eventListeners: null,