Fix syntax error

lib/html/src/Isolates.dart

 // Copyright (c) 2012, 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.
 
 _serialize(var message) {
   return new _JsSerializer().traverse(message);
 }
 
 class JsProxy {
   SendPortSync _port;
   final _id;
 
   JsProxy._internal(this._port, this._id);
 
   noSuchMethod(method, args) {
     var result = _port.callSync([_id, method, args]);
     switch (result[0]) {
       case 'return': return result[1];
       case 'exception': throw result[1];
       case 'none': throw new NoSuchMethodException(this, method, args);
       default: throw 'Invalid return value';
     }
   }
 }
 
 int _localNextElementId = 0;
 
 const _DART_ID = 'data-dart_id';
 
-var _elementId(Element e) {
+_elementId(Element e) {
   if (e.attributes.containsKey(_DART_ID)) return e.attributes[_DART_ID];
   var id = '$_isolateId-${_localNextElementId++}';
   e.attributes[_DART_ID] = id;
   return id;
 }
 
 Element _getElement(var id) {
   var list = queryAll('[$_DART_ID="$id"]');
   if (list.length > 1) throw 'Non unique ID: $id';
   if (list.length == 0) {
@@ skipping 327 matching lines @@
   }
 }
 
 get _isolateId => ReceivePortSync._isolateId;
 
 void _dispatchEvent(String receiver, var message) {
   var event = document.$dom_createEvent('TextEvent');
   event.initTextEvent(receiver, false, false, window, JSON.stringify(message));
   window.$dom_dispatchEvent(event);
 }