Add getId() method for ol.render.Feature

src/ol/render/feature.js

@@ -16,14 +16,21 @@ goog.require('ol.geom.GeometryType');
  *     to be right-handed for polygons.
  * @param {Array.<number>|Array.<Array.<number>>} ends Ends or Endss.
  * @param {Object.<string, *>} properties Properties.
+ * @param {number|string|undefined} id Feature id.
  */
-ol.render.Feature = function(type, flatCoordinates, ends, properties) {
+ol.render.Feature = function(type, flatCoordinates, ends, properties, id) {
   /**
    * @private
    * @type {ol.Extent|undefined}
    */
   this.extent_;
 
+  /**
+   * @private
+   * @type {number|string|undefined}
+   */
+  this.id_ = id;
+
   /**
    * @private
    * @type {ol.geom.GeometryType}
@@ -85,6 +92,16 @@ ol.render.Feature.prototype.getExtent = function() {
   return this.extent_;
 };
 
+/**
+ * Get the feature identifier.  This is a stable identifier for the feature and
+ * is set when reading data from a remote source.
+ * @return {number|string|undefined} Id.
+ * @api
+ */
+ol.render.Feature.prototype.getId = function() {
+  return this.id_;
+};
+
 
 /**
  * @return {Array.<number>} Flat coordinates.