Remove support for attribute event listeners.

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

 
 class WorkerContext native "WorkerContext" {
 
   WorkerLocation location;
 
   WorkerNavigator navigator;
 
-  EventListener onerror;
-
   WorkerContext self;
 
   NotificationCenter webkitNotifications;
 
   DOMURL webkitURL;
 
   void addEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   void clearInterval(int handle) native;
 
   void clearTimeout(int handle) native;
 
   void close() native;
 
   bool dispatchEvent(Event evt) native;
 
   void importScripts() native;
 
   void removeEventListener(String type, EventListener listener, [bool useCapture = null]) native;
 
   int setInterval(TimeoutHandler handler, int timeout) native;
 
   int setTimeout(TimeoutHandler handler, int timeout) native;
 
   var dartObjectLocalStorage;
 
   String get typeName() native;
 }