Respect the tileSize option for XYZ grids

src/ol/tilegrid/xyztilegrid.js

@@ -24,18 +24,16 @@ goog.require('ol.tilegrid.TileGrid');
  * @api
  */
 ol.tilegrid.XYZ = function(options) {
-  // TODO: accept a tileSize option
-  var tileSize = ol.DEFAULT_TILE_SIZE;
   var extent = goog.isDef(options.extent) ?
       options.extent : ol.proj.EPSG3857.EXTENT;
   var resolutions = ol.tilegrid.resolutionsFromExtent(
-      extent, options.maxZoom, tileSize);
+      extent, options.maxZoom, options.tileSize);
 
   goog.base(this, {
     minZoom: options.minZoom,
     origin: ol.extent.getCorner(extent, ol.extent.Corner.TOP_LEFT),
     resolutions: resolutions,
-    tileSize: tileSize
+    tileSize: options.tileSize
   });
 
 };