Re-introducing tileLoadingDelay.

Only use it if no native requestAnimationFrame function is available. This should improve performance on mobile devices.

lib/OpenLayers/Animation.js

@@ -15,6 +15,16 @@
  */
 OpenLayers.Animation = (function(window) {
     
+    /**
+     * Property: isNative
+     * {Boolean} true if a native requestAnimationFrame function is available
+     */
+    var isNative = !!(window.requestAnimationFrame ||
+        window.webkitRequestAnimationFrame ||
+        window.mozRequestAnimationFrame ||
+        window.oRequestAnimationFrame ||
+        window.msRequestAnimationFrame);
+    
     /**
      * Function: requestFrame
      * Schedule a function to be called at the next available animation frame.
@@ -89,6 +99,7 @@ OpenLayers.Animation = (function(window) {
     }
     
     return {
+        isNative: isNative,
         requestFrame: requestFrame,
         start: start,
         stop: stop