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

client/html/src/XMLHttpRequest.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.
 
 interface XMLHttpRequestEvents extends Events {
   EventListenerList get abort();
   EventListenerList get error();
   EventListenerList get load();
   EventListenerList get loadStart();
   EventListenerList get progress();
   EventListenerList get readyStateChange();
 }
 
-interface XMLHttpRequest extends EventTarget factory XMLHttpRequestWrappingImplementation {
+interface XMLHttpRequest extends EventTarget default XMLHttpRequestWrappingImplementation {
   static final int DONE = 4;
 
   static final int HEADERS_RECEIVED = 2;
 
   static final int LOADING = 3;
 
   static final int OPENED = 1;
 
   static final int UNSENT = 0;
 
@@ skipping 32 matching lines @@
   void open(String method, String url, bool async, [String user, String password]);
 
   void overrideMimeType(String mime);
 
   void send([String data]);
 
   void setRequestHeader(String header, String value);
 
   XMLHttpRequestEvents get on();
 }