Provide the ability to get the layer name from a MapQuest source

src/ol/source/mapquestsource.js

@@ -24,10 +24,17 @@ ol.source.MapQuest = function(opt_options) {
 
   var layerConfig = ol.source.MapQuestConfig[options.layer];
 
+  /**
+   * Layer. Possible values are `osm`, `sat`, and `hyb`.
+   * @type {string}
+   * @private
+   */
+  this.layer_ = options.layer;
+
   var protocol = ol.IS_HTTPS ? 'https:' : 'http:';
   var url = goog.isDef(options.url) ? options.url :
       protocol + '//otile{1-4}-s.mqcdn.com/tiles/1.0.0/' +
-      options.layer + '/{z}/{x}/{y}.jpg';
+      this.layer_ + '/{z}/{x}/{y}.jpg';
 
   goog.base(this, {
     attributions: layerConfig.attributions,
@@ -81,3 +88,12 @@ ol.source.MapQuestConfig = {
     ]
   }
 };
+
+
+/**
+ * @return {string} Layer.
+ * @api
+ */
+ol.source.MapQuest.prototype.getLayer = function() {
+  return this.layer_;
+};