Allow drag and drop interaction to be configured with a source

src/ol/interaction/draganddrop.js

@@ -49,6 +49,12 @@ ol.interaction.DragAndDrop = function(opt_options) {
    */
   this.dropListenKeys_ = null;
 
+  /**
+   * @private
+   * @type {ol.source.Vector}
+   */
+  this.source_ = options.source || null;
+
   /**
    * @private
    * @type {Element}
@@ -122,6 +128,10 @@ ol.interaction.DragAndDrop.prototype.handleResult_ = function(file, event) {
       break;
     }
   }
+  if (this.source_) {
+    this.source_.clear();
+    this.source_.addFeatures(features);
+  }
   this.dispatchEvent(
       new ol.interaction.DragAndDrop.Event(
           ol.interaction.DragAndDrop.EventType_.ADD_FEATURES, file,