Caching array length instead of accessing it with each iteration. r=crschmidt (closes #1636)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@7627 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/HTTPRequest.js

@@ -160,7 +160,7 @@ OpenLayers.Layer.HTTPRequest = OpenLayers.Class(OpenLayers.Layer, {
      */
     selectUrl: function(paramString, urls) {
         var product = 1;
-        for (var i = 0; i < paramString.length; i++) { 
+        for (var i=0, len=paramString.length; i<len; i++) { 
             product *= paramString.charCodeAt(i) * this.URL_HASH_FACTOR; 
             product -= Math.floor(product); 
         }