Safely wrap window.top in frog dom.

client/dom/generated/src/wrapping/_DirectoryReaderWrappingImplementation.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 _DirectoryReaderWrappingImplementation extends DOMWrapperBase implements DirectoryReader {
   _DirectoryReaderWrappingImplementation() : super() {}
 
   static create__DirectoryReaderWrappingImplementation() native {
     return new _DirectoryReaderWrappingImplementation();
   }
 
   void readEntries(EntriesCallback successCallback, [ErrorCallback errorCallback = null]) {
-    if (errorCallback === null) {
-      _readEntries(this, successCallback);
-      return;
-    } else {
-      _readEntries_2(this, successCallback, errorCallback);
-      return;
-    }
+    _readEntries(this, successCallback, errorCallback);
+    return;
   }
-  static void _readEntries(receiver, successCallback) native;
-  static void _readEntries_2(receiver, successCallback, errorCallback) native;
+  static void _readEntries(receiver, successCallback, errorCallback) native;
 
   String get typeName() { return "DirectoryReader"; }
 }