Remove generated directories with 100s of files.

client/html/generated/html/dartium/NotificationCenter.dart

-
-class _NotificationCenterImpl extends _DOMTypeBase implements NotificationCenter {
-  _NotificationCenterImpl._wrap(ptr) : super._wrap(ptr);
-
-  int checkPermission() {
-    return _wrap(_ptr.checkPermission());
-  }
-
-  Notification createHTMLNotification(String url) {
-    return _wrap(_ptr.createHTMLNotification(_unwrap(url)));
-  }
-
-  Notification createNotification(String iconUrl, String title, String body) {
-    return _wrap(_ptr.createNotification(_unwrap(iconUrl), _unwrap(title), _unwrap(body)));
-  }
-
-  void requestPermission(VoidCallback callback) {
-    _ptr.requestPermission(_unwrap(callback));
-    return;
-  }
-}