Return type of decodeUtf8AsIterable and variants. The Iterable type provides an iterator on demand and the iterator will only translate bytes as requested by the user of the iterator. (Note: results are not cached.)

class IterableUtf8Decoder implements Iterable<int> {
  final List<int> bytes;
  final int offset;
  final int length;
  final int replacementCodepoint;

  IterableUtf8Decoder(this.bytes, [this.offset = 0, this.length = null,
      this.replacementCodepoint = UNICODE_REPLACEMENT_CHARACTER_CODEPOINT]);

  Utf8Decoder iterator() => new Utf8Decoder(bytes, offset, length,
          replacementCodepoint);
}