anchor.diff:  // This returns a 2 element list.  The first is the number of currently
   // live proxies.  The second is the total number of proxies ever
   // allocated.
  -List _proxyCountJavaScript() {
  -  return _jsPortProxyCount.callSync([]);
  -}
  +List _proxyCountJavaScript() => _jsPortProxyCount.callSync([]);
   
   /**
    * Returns the number of allocated proxy objects matching the given
  
positive.code: /**
   * Check if [proxy] is instance of [type].
   */
  bool instanceof(Proxy proxy, type) {
    return _jsPortInstanceof.callSync([proxy, type].map(_serialize).toList());
  }
  
  /**
   * Delete the [name] property of [proxy].
   */
  void deleteProperty(Proxy proxy, String name) {
    _jsPortDeleteProperty.callSync([proxy, name].map(_serialize).toList());
  }
  
  /**
  
negative.code:    * explicitly disposed to avoid memory leaks.
     */
    Callback.many(Function f, {bool withThis: false}) {
      _callback = (List args) =>
          Function.apply(f, withThis ? args : args.skip(1).toList());
      _initialize(true);
    }
  }
  