Add chunked conversion to converters.

tests/lib/convert/chunked_conversion_utf84_test.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.
+
+import "package:expect/expect.dart";
+import 'dart:convert';
+import 'unicode_tests.dart';
+
+String decode(List<int> bytes, int chunkSize) {
+  StringBuffer buffer = new StringBuffer();
+  // Use a non-chunked interface.
+  String result;
+  ChunkedConversionSink chunkedSink =
+      StringConversionSink.INTERFACE.createSink((decoded) {
+        result = decoded;
+      });
+  var byteSink = new Utf8Decoder().startChunkedConversion(chunkedSink);
+  int i = 0;
+  while (i < bytes.length) {
+    List nextChunk = [];
+    for (int j = 0; j < chunkSize; j++) {
+      if (i < bytes.length) {
+        nextChunk.add(bytes[i]);
+        i++;
+      }
+    }
+    byteSink.add(nextChunk);
+  }
+  byteSink.close();
+  return result;
+}
+
+main() {
+  for (var test in UNICODE_TESTS) {
+    var bytes = test[0];
+    var expected = test[1];
+    Expect.stringEquals(expected, decode(bytes, 1));
+    Expect.stringEquals(expected, decode(bytes, 2));
+    Expect.stringEquals(expected, decode(bytes, 3));
+    Expect.stringEquals(expected, decode(bytes, 4));
+  }
+}