Remove support for attribute event listeners.

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

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // WARNING: Do not edit - generated code.
 
 interface WorkerGlobalScope {
 
   WorkerLocation get location();
 
   void set location(WorkerLocation value);
 
   WorkerNavigator get navigator();
 
   void set navigator(WorkerNavigator value);
 
-  EventListener get onerror();
-
-  void set onerror(EventListener value);
-
   WorkerContext get self();
 
   void set self(WorkerContext value);
 
   NotificationCenter get webkitNotifications();
 
   DOMURL get webkitURL();
 
   void addEventListener(String type, EventListener listener, [bool useCapture]);
 
   void clearInterval(int handle);
 
   void clearTimeout(int handle);
 
   void close();
 
   bool dispatchEvent(Event evt);
 
   void importScripts();
 
   void removeEventListener(String type, EventListener listener, [bool useCapture]);
 
   int setInterval(TimeoutHandler handler, int timeout);
 
   int setTimeout(TimeoutHandler handler, int timeout);
 }
 
 interface WorkerContext extends WorkerGlobalScope {
 }