Remove generated directories with 100s of files.

client/dom/generated/src/frog/_TextTrackCueFactoryProvider.dart

-// Copyright (c) 2012, 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.
-
-class _TextTrackCueFactoryProvider {
-  factory TextTrackCue(String id, num startTime, num endTime, String text,
-                       [String settings, bool pauseOnExit]) native
-'''
-if (settings == null)
-  return new TextTrackCue(id, startTime, endTime, text);
-if (pauseOnExit == null)
-  return new TextTrackCue(id, startTime, endTime, text, settings);
-return new TextTrackCue(id, startTime, endTime, text, settings, pauseOnExit);
-''';
-}