Avoid runtime type errors in checked mode for ChunkedConverters.

sdk/lib/io/data_transformer.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 /**
  * Exposes ZLib options for input parameters.
  *
  * See http://www.zlib.net/manual.html for more documentation.
@@ skipping 257 matching lines @@
    * Get a [ZLibDecoder] for decoding `GZip` compressed data.
    */
   ZLibDecoder get decoder =>
       new ZLibDecoder(windowBits: windowBits, dictionary: dictionary, raw: raw);
 }
 
 /**
  * The [ZLibEncoder] encoder is used by [ZLibCodec] and [GZipCodec] to compress
  * data.
  */
-class ZLibEncoder extends Converter<List<int>, List<int>> {
+class ZLibEncoder extends Converter<List<int>, List<int>>
+    implements ChunkedConverter<List<int>, List<int>, List<int>, List<int>> {
+
   /**
    * When true, `GZip` frames will be added to the compressed data.
    */
   final bool gzip;
 
   /**
    * The compression-[level] can be set in the range of `-1..9`, with `6` being
    * the default compression level. Levels above `6` will have higher
    * compression rates at the cost of more CPU and memory usage. Levels below
    * `6` will use less CPU and memory at the cost of lower compression rates.
@@ skipping 289 matching lines @@
 }
 
 void _validateZLibStrategy(int strategy) {
   const strategies = const <int>[ZLibOption.STRATEGY_FILTERED,
       ZLibOption.STRATEGY_HUFFMAN_ONLY, ZLibOption.STRATEGY_RLE,
       ZLibOption.STRATEGY_FIXED, ZLibOption.STRATEGY_DEFAULT];
   if (strategies.indexOf(strategy) == -1) {
     throw new ArgumentError("Unsupported 'strategy'");
   }
 }