message: [tf.data] Use `get_legacy_output_classes()` in `ConcatenateDataset` and `WindowDataset`.
diff: @@ -2540,7 +2540,7 @@ class ConcatenateDataset(DatasetV2):
  "Two datasets to concatenate have different types %s and %s" %
  (output_types, get_legacy_output_types(dataset_to_concatenate)))
  - output_classes = input_dataset.output_classes
  + output_classes = get_legacy_output_classes(input_dataset)
  if output_classes != get_legacy_output_classes(dataset_to_concatenate):
  raise TypeError(
  "Two datasets to concatenate have different classes %s and %s" %
  @@ -3209,7 +3209,7 @@ class WindowDataset(UnaryDataset):
  self._drop_remainder = ops.convert_to_tensor(
  drop_remainder, dtype=dtypes.bool, name="drop_remainder")
  nest_of_structures = nest.pack_sequence_as(
  - input_dataset.output_classes,
  + get_legacy_output_classes(input_dataset),
  [
  DatasetStructure(structure_lib.convert_legacy_structure(
  output_type, output_shape, output_class))
  