Add preload example

examples/preload.js

@@ -0,0 +1,40 @@
+goog.require('ol.Coordinate');
+goog.require('ol.Map');
+goog.require('ol.RendererHints');
+goog.require('ol.View2D');
+goog.require('ol.layer.TileLayer');
+goog.require('ol.source.BingMaps');
+
+
+var map1 = new ol.Map({
+  layers: [
+    new ol.layer.TileLayer({
+      preload: true,
+      source: new ol.source.BingMaps({
+        key: 'AgtFlPYDnymLEe9zJ5PCkghbNiFZE9aAtTy3mPaEnEBXqLHtFuTcKoZ-miMC3w7R',
+        style: 'Aerial'
+      })
+    })
+  ],
+  renderers: ol.RendererHints.createFromQueryData(),
+  target: 'map1',
+  view: new ol.View2D({
+    center: new ol.Coordinate(-4808600, -2620936),
+    zoom: 8
+  })
+});
+
+var map2 = new ol.Map({
+  layers: [
+    new ol.layer.TileLayer({
+      preload: false,
+      source: new ol.source.BingMaps({
+        key: 'AgtFlPYDnymLEe9zJ5PCkghbNiFZE9aAtTy3mPaEnEBXqLHtFuTcKoZ-miMC3w7R',
+        style: 'AerialWithLabels'
+      })
+    })
+  ],
+  renderers: ol.RendererHints.createFromQueryData(),
+  target: 'map2'
+});
+map2.bindTo('view', map1);