Switch from interfaces to abstract classes in dart:io.

runtime/bin/list_stream.dart

 // Copyright (c) 2012, 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.
 
 /**
  * [ListInputStream] makes it possible to use the [InputStream]
  * interface to stream over data that is received in chunks as lists
  * of integers.
  *
  * When a new list of integers is received it can be written to the
  * [ListInputStream] using the [write] method. The [markEndOfStream]
  * method must be called when the last data has been written to the
  * [ListInputStream].
  */
-interface ListInputStream extends InputStream default _ListInputStream {
+abstract class ListInputStream implements InputStream {
   /**
    * Create an empty [ListInputStream] to which data can be written
    * using the [write] method.
    */
-  ListInputStream();
+  factory ListInputStream() =>  new _ListInputStream();
 
   /**
    * Write more data to be streamed over to the [ListInputStream].
    */
   void write(List<int> data);
 
   /**
    * Notify the [ListInputStream] that no more data will be written to
    * it.
    */
   void markEndOfStream();
 }
 
 
 /**
  * [ListOutputStream] makes it possible to use the [OutputStream]
  * interface to write data to a [List] of integers.
  */
-interface ListOutputStream extends OutputStream default _ListOutputStream {
+abstract class ListOutputStream implements OutputStream {
   /**
    * Create a [ListOutputStream].
    */
-  ListOutputStream();
+  factory ListOutputStream() => new _ListOutputStream();
 
   /**
    * Reads all available data from the stream. If no data is available `null`
    * will be returned.
    */
   List<int> read();
 
   /**
    * Sets the handler that gets called when data is available.
    */
   void set onData(void callback());
 }