Remove support for attribute event listeners.

client/dom/generated/src/wrapping/_WorkerWrappingImplementation.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.
 
 class _WorkerWrappingImplementation extends _AbstractWorkerWrappingImplementation implements Worker {
   _WorkerWrappingImplementation() : super() {}
 
   static create__WorkerWrappingImplementation() native {
     return new _WorkerWrappingImplementation();
   }
 
-  EventListener get onmessage() { return _get_onmessage(this); }
-  static EventListener _get_onmessage(var _this) native;
-
-  void set onmessage(EventListener value) { _set_onmessage(this, value); }
-  static void _set_onmessage(var _this, EventListener value) native;
-
   void postMessage(String message, [List messagePorts = null]) {
     if (messagePorts === null) {
       _postMessage(this, message);
       return;
     } else {
       _postMessage_2(this, message, messagePorts);
       return;
     }
   }
   static void _postMessage(receiver, message) native;
@@ skipping 12 matching lines @@
     } else {
       _webkitPostMessage_2(this, message, messagePorts);
       return;
     }
   }
   static void _webkitPostMessage(receiver, message) native;
   static void _webkitPostMessage_2(receiver, message, messagePorts) native;
 
   String get typeName() { return "Worker"; }
 }