Make the package strong-mode clean.

lib/src/percent/encoder.dart

 // Copyright (c) 2015, 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.
 
 library convert.percent.encoder;
 
 import 'dart:convert';
 
 import 'package:charcode/ascii.dart';
 
 /// The canonical instance of [PercentEncoder].
 const percentEncoder = const PercentEncoder._();
 
 /// A converter that encodes byte arrays into percent-encoded strings.
 ///
 /// [encoder] encodes all bytes other than ASCII letters, decimal digits, or one
 /// of `-._~`. This matches the behavior of [Uri.encodeQueryComponent] except
 /// that it doesn't encode `0x20` bytes to the `+` character.
 ///
 /// This will throw a [RangeError] if the byte array has any digits that don't
 /// fit in the gamut of a byte.
-class PercentEncoder extends Converter<List<int>, String> {
+class PercentEncoder
+    extends ChunkedConverter<List<int>, String, List<int>, String> {
   const PercentEncoder._();
 
   String convert(List<int> bytes) => _convert(bytes, 0, bytes.length);
 
   ByteConversionSink startChunkedConversion(Sink<String> sink) =>
       new _PercentEncoderSink(sink);
 }
 
 /// A conversion sink for chunked percentadecimal encoding.
 class _PercentEncoderSink extends ByteConversionSinkBase {
@@ skipping 62 matching lines @@
         "Invalid byte ${byte < 0 ? "-" : ""}0x${byte.abs().toRadixString(16)}.",
         bytes, i);
   }
 
   throw 'unreachable';
 }
 
 /// Returns the ASCII/Unicode code unit corresponding to the hexadecimal digit
 /// [digit].
 int _codeUnitForDigit(int digit) => digit < 10 ? digit + $0 : digit + $A - 10;