Make ReceivePort an abstract class.

sdk/lib/isolate/base.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.
 
 class IsolateSpawnException implements Exception {
   const IsolateSpawnException(String this._s);
   String toString() => "IsolateSpawnException: '$_s'";
   final String _s;
 }
 
@@ skipping 87 matching lines @@
 
 /**
  * [ReceivePort]s, together with [SendPort]s, are the only means of
  * communication between isolates. [ReceivePort]s have a [:toSendPort:] method
  * which returns a [SendPort]. Any message that is sent through this [SendPort]
  * is delivered to the [ReceivePort] it has been created from. There, they are
  * dispatched to the callback that has been registered on the receive port.
  *
  * A [ReceivePort] may have many [SendPort]s.
  */
-interface ReceivePort default _ReceivePortFactory {
+abstract class ReceivePort {
 
   /**
    * Opens a long-lived port for receiving messages. The returned port
    * must be explicitly closed through [ReceivePort.close].
    */
-  ReceivePort();
+  external factory ReceivePort();
 
   /**
    * Sets up a callback function for receiving pending or future
    * messages on this receive port.
    */
   void receive(void callback(var message, SendPort replyTo));
 
   /**
    * Closes this receive port immediately. Pending messages will not
    * be processed and it is impossible to re-open the port. Single-shot
@@ skipping 10 matching lines @@
   SendPort toSendPort();
 
 }
 
 // TODO(kasperl): Document this.
 abstract class SendPortSync {
 
   callSync(var message);
 
 }
-
-class _ReceivePortFactory {
-  external factory ReceivePort();
-}