Make the package strong-mode clean.

lib/src/percent/encoder.dart

Index: lib/src/percent/encoder.dart
diff --git a/lib/src/percent/encoder.dart b/lib/src/percent/encoder.dart
index c7817609e81c8adc762619d3d7ebd253d4ae7daa..b4cf1a199725fc14b129eb33db4b8b233b1c0c6a 100644
--- a/lib/src/percent/encoder.dart
+++ b/lib/src/percent/encoder.dart
@@ -19,7 +19,8 @@ const percentEncoder = const PercentEncoder._();
 ///
 /// 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);