don't clone the size from map.getSize(). r=elemoine (closes #2603)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@10377 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/Grid.js

@@ -207,7 +207,7 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
      */
     setTileSize: function(size) { 
         if (this.singleTile) {
-            size = this.map.getSize().clone();
+            size = this.map.getSize();
             size.h = parseInt(size.h * this.ratio);
             size.w = parseInt(size.w * this.ratio);
         }