Remove generated directories with 100s of files.

client/dom/generated/src/wrapping/_MediaStreamTrackListWrappingImplementation.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 _MediaStreamTrackListWrappingImplementation extends DOMWrapperBase implements MediaStreamTrackList {
-  _MediaStreamTrackListWrappingImplementation() : super() {}
-
-  static create__MediaStreamTrackListWrappingImplementation() native {
-    return new _MediaStreamTrackListWrappingImplementation();
-  }
-
-  int get length() { return _get_length(this); }
-  static int _get_length(var _this) native;
-
-  MediaStreamTrack item(int index) {
-    return _item(this, index);
-  }
-  static MediaStreamTrack _item(receiver, index) native;
-
-  String get typeName() { return "MediaStreamTrackList"; }
-}