Add ol.render.IRender#drawAsync

src/ol/render/irender.js

@@ -11,6 +11,14 @@ ol.render.IRender = function() {
 };
 
 
+/**
+ * @param {number} zIndex Z index.
+ * @param {function(ol.render.canvas.Immediate)} callback Callback.
+ */
+ol.render.IRender.prototype.drawAsync = function(zIndex, callback) {
+};
+
+
 /**
  * @param {ol.Feature} feature Feature.
  * @param {ol.style.Style} style Style.