Use de-facto standard 512px tile size for vectortile layers

examples/mapbox-vector-tiles.js

@@ -23,8 +23,8 @@ var map = new ol.Map({
           '© <a href="https://www.openstreetmap.org/copyright">' +
           'OpenStreetMap contributors</a>',
         format: new ol.format.MVT(),
-        tileGrid: ol.tilegrid.createXYZ({maxZoom: 22}),
-        tilePixelRatio: 16,
+        tileGrid: ol.tilegrid.createXYZ({tileSize: 512, maxZoom: 22}),
+        tilePixelRatio: 8,
         url: 'https://{a-d}.tiles.mapbox.com/v4/mapbox.mapbox-streets-v6/' +
             '{z}/{x}/{y}.vector.pbf?access_token=' + key
       }),

examples/osm-vector-tiles.js

@@ -70,7 +70,7 @@ var map = new ol.Map({
           layerName: 'layer',
           layers: ['water', 'roads', 'buildings']
         }),
-        tileGrid: ol.tilegrid.createXYZ({maxZoom: 19}),
+        tileGrid: ol.tilegrid.createXYZ({tileSize: 512, maxZoom: 19}),
         url: 'https://tile.mapzen.com/mapzen/vector/v1/all/{z}/{x}/{y}.topojson?api_key=' + key
       }),
       style: function(feature, resolution) {