Make dart:convert strong mode clean.

tests/lib/convert/chunked_conversion1_test.dart

Index: tests/lib/convert/chunked_conversion1_test.dart
diff --git a/tests/lib/convert/chunked_conversion1_test.dart b/tests/lib/convert/chunked_conversion1_test.dart
index 3c84b3e4d377003dd07e175148fdb0cf9ed3a356..0bbe44b7f700e48d42426c1c1ee62fe7cbf08b85 100644
--- a/tests/lib/convert/chunked_conversion1_test.dart
+++ b/tests/lib/convert/chunked_conversion1_test.dart
@@ -54,8 +54,7 @@ class BoolAdapterSink extends MyChunkedBoolSink {
   specialB(o) => add(o);
 }
 
-class IntBoolConverter1 extends
-    ChunkedConverter<List<int>, List<bool>, int, bool> {
+class IntBoolConverter1 extends Converter<List<int>, List<bool>> {
   List<bool> convert(List<int> input) => input.map((x) => x > 0).toList();
 
   startChunkedConversion(sink) {
@@ -64,8 +63,7 @@ class IntBoolConverter1 extends
   }
 }
 
-class BoolIntConverter1 extends
-    ChunkedConverter<List<bool>, List<int>, bool, int> {
+class BoolIntConverter1 extends Converter<List<bool>, List<int>> {
   List<int> convert(List<bool> input) => input.map((x) => x ? 1 : 0).toList();
 
   startChunkedConversion(sink) {
@@ -106,7 +104,7 @@ class BoolIntConverter1Sink extends MyChunkedBoolSink {
   close() => outSink.close();
 }
 
-class IdentityConverter extends ChunkedConverter {
+class IdentityConverter extends Converter {
   convert(x) => x;
 
   startChunkedConversion(sink) {