Generate callbacks as typedefs.

client/dom/generated/src/wrapping/_DatabaseCallbackWrappingImplementation.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 _DatabaseCallbackWrappingImplementation extends DOMWrapperBase implements DatabaseCallback {
-  _DatabaseCallbackWrappingImplementation() : super() {}
-
-  static create__DatabaseCallbackWrappingImplementation() native {
-    return new _DatabaseCallbackWrappingImplementation();
-  }
-
-  bool handleEvent(var database) {
-    if (database is Database) {
-      return _handleEvent(this, database);
-    } else {
-      if (database is DatabaseSync) {
-        return _handleEvent_2(this, database);
-      }
-    }
-    throw "Incorrect number or type of arguments";
-  }
-  static bool _handleEvent(receiver, database) native;
-  static bool _handleEvent_2(receiver, database) native;
-
-  String get typeName() { return "DatabaseCallback"; }
-}