add a tileAnimation map option

lib/OpenLayers/Map.js

@@ -395,6 +395,14 @@ OpenLayers.Map = OpenLayers.Class({
      *     the popup from getting too close to the map border.
      */
     paddingForPopups : null,
+
+    /**
+     * APIProperty: tileAnimation
+     * {Boolean} If set to true the olMapTileAnim class is assigned to the
+     *     map div. This, with OpenLayers' default CSS, results in fade-in
+     *     effects when image tiles are displayed.
+     */
+    tileAnimation: true,
     
     /**
      * Property: minPx
@@ -500,6 +508,9 @@ OpenLayers.Map = OpenLayers.Class({
         }
         
         OpenLayers.Element.addClass(this.div, 'olMap');
+        if (this.tileAnimation) {
+            OpenLayers.Element.addClass(this.div, 'olMapTileAnim');
+        }
 
         // the viewPortDiv is the outermost div we modify
         var id = this.id + "_OpenLayers_ViewPort";