fix: use _start not start function

Author: sbeleidy

file-fire-drop.html

@@ -119,7 +119,7 @@
     },
 
     _instantLoad: function(event){
-      this.start(event);
+      this._start(event);
       if(this.instant){
         var reader = new FileReader();
         reader.onload = function (data) {