Introduce class Sink<T>.

sdk/lib/convert/byte_conversion.dart

Index: sdk/lib/convert/byte_conversion.dart
diff --git a/sdk/lib/convert/byte_conversion.dart b/sdk/lib/convert/byte_conversion.dart
index 18da9d3a4e77a291374f2aa081ef1ae9b437b13a..bb94991fefc9aee9498a1c4aaf75fb80bc338152 100644
--- a/sdk/lib/convert/byte_conversion.dart
+++ b/sdk/lib/convert/byte_conversion.dart
@@ -19,7 +19,7 @@ abstract class ByteConversionSink extends ChunkedConversionSink<List<int>> {
   ByteConversionSink();
   factory ByteConversionSink.withCallback(void callback(List<int> accumulated))
       = _ByteCallbackSink;
-  factory ByteConversionSink.from(ChunkedConversionSink<List<int>> sink)
+  factory ByteConversionSink.from(Sink<List<int>> sink)
       = _ByteAdapterSink;
 
   /**
@@ -54,13 +54,13 @@ abstract class ByteConversionSinkBase extends ByteConversionSink {
 }
 
 /**
- * This class adapts a simple [ChunkedConversionSink] to a [ByteConversionSink].
+ * This class adapts a simple [Sink] to a [ByteConversionSink].
  *
  * All additional methods of the [ByteConversionSink] (compared to the
  * ChunkedConversionSink) are redirected to the `add` method.
  */
 class _ByteAdapterSink extends ByteConversionSinkBase {
-  final ChunkedConversionSink<List<int>> _sink;
+  final Sink<List<int>> _sink;
 
   _ByteAdapterSink(this._sink);