Remove generated directories with 100s of files.

client/dom/generated/src/wrapping/_WebGLContextEventWrappingImplementation.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 _WebGLContextEventWrappingImplementation extends _EventWrappingImplementation implements WebGLContextEvent {
-  _WebGLContextEventWrappingImplementation() : super() {}
-
-  static create__WebGLContextEventWrappingImplementation() native {
-    return new _WebGLContextEventWrappingImplementation();
-  }
-
-  String get statusMessage() { return _get_statusMessage(this); }
-  static String _get_statusMessage(var _this) native;
-
-  String get typeName() { return "WebGLContextEvent"; }
-}