Let EventTarget be a base class in the frog dom.

client/dom/generated/src/frog/DOMApplicationCache.dart

 
-class _DOMApplicationCacheJs extends _DOMTypeJs implements DOMApplicationCache native "*DOMApplicationCache" {
+class _DOMApplicationCacheJs extends _EventTargetJs implements DOMApplicationCache native "*DOMApplicationCache" {
 
   static final int CHECKING = 2;
 
   static final int DOWNLOADING = 3;
 
   static final int IDLE = 1;
 
   static final int OBSOLETE = 5;
 
   static final int UNCACHED = 0;
 
   static final int UPDATEREADY = 4;
 
   final int status;
 
   void abort() native;
 
   void addEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   bool dispatchEvent(_EventJs evt) native;
 
   void removeEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   void swapCache() native;
 
   void update() native;
 }