Add transformer support to Converters.

tests/lib/convert/chunked_conversion2_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 'dart:convert';
+
+import 'package:expect/expect.dart';
+
+// Test that the String and ByteConversionSinks make a copy when they need to
+// adapt.
+
+class MyByteSink extends ByteConversionSinkBase {
+  var accumulator = [];
+  add(List<int> bytes) {
+    accumulator.add(bytes);
+  }
+  close() {}
+}
+
+void testBase() {
+  var byteSink = new MyByteSink();
+  var bytes = [1];
+  byteSink.addSlice(bytes, 0, 1, false);
+  bytes[0] = 2;
+  byteSink.addSlice(bytes, 0, 1, true);
+  Expect.equals(1, byteSink.accumulator[0][0]);
+  Expect.equals(2, byteSink.accumulator[1][0]);
+}
+
+class MyChunkedSink extends ChunkedConversionSink {
+  var accumulator = [];
+  add(List<int> bytes) {
+    accumulator.add(bytes);
+  }
+  close() {}
+}
+
+void testAdapter() {
+  var chunkedSink = new MyChunkedSink();
+  var byteSink = new ByteConversionSink.from(chunkedSink);
+  var bytes = [1];
+  byteSink.addSlice(bytes, 0, 1, false);
+  bytes[0] = 2;
+  byteSink.addSlice(bytes, 0, 1, true);
+  Expect.equals(1, chunkedSink.accumulator[0][0]);
+  Expect.equals(2, chunkedSink.accumulator[1][0]);
+}
+
+void main() {
+  testBase();
+  testAdapter();
+}