Remove generated directories with 100s of files.

client/dom/generated/src/wrapping/_DOMFormDataWrappingImplementation.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 _DOMFormDataWrappingImplementation extends DOMWrapperBase implements DOMFormData {
-  _DOMFormDataWrappingImplementation() : super() {}
-
-  static create__DOMFormDataWrappingImplementation() native {
-    return new _DOMFormDataWrappingImplementation();
-  }
-
-  void append(String name, String value, String filename) {
-    _append(this, name, value, filename);
-    return;
-  }
-  static void _append(receiver, name, value, filename) native;
-
-  String get typeName() { return "DOMFormData"; }
-}