Moves over remaining .dart code references to 'factory' in interface declartions to 'default'

samples/belay/bcap/src/BcapTunnel.dart

 // Copyright (c) 2011, 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 ContinuationPair {
   final Success sk;
   final Failure fk;
   const ContinuationPair(this.sk, this.fk);
 }
 
@@ skipping 111 matching lines @@
 
   PongMsg() : super() { }
 
   Map toJSON() =>  { 'op': 'pong' };
   
   void respond(BcapTunnelImpl tunnel) {
     // nothing to do
   }
 }
 
-interface BcapTunnel extends BcapServerInterface factory BcapTunnelImpl {
+interface BcapTunnel extends BcapServerInterface default BcapTunnelImpl {
   
   void sendOutpost(var msg);
 
   BcapTunnel(BelayPort port, Resolver resolver, Function outpostHandler);
 }
 
 typedef void OutpostHandler(Map outpostData);
 
 class BcapTunnelImpl implements BcapServerInterface {
 
@@ skipping 21 matching lines @@
     });
   }
 
   void sendOutpost(data) {
     port.postMessage((new OutpostMsg(data)).toJSON());
   }
 }