Add ol.Layer.isReady

src/ol/base/layer.js

@@ -107,6 +107,14 @@ ol.Layer.prototype.getVisible = function() {
 };
 
 
+/**
+ * @return {boolean} Is ready.
+ */
+ol.Layer.prototype.isReady = function() {
+  return this.getStore().isReady();
+};
+
+
 /**
  * @param {number} brightness Brightness.
  */