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

client/html/src/MouseEvent.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 MouseEvent extends UIEvent factory MouseEventWrappingImplementation {
+interface MouseEvent extends UIEvent default MouseEventWrappingImplementation {
 
   MouseEvent(String type, Window view, int detail, int screenX, int screenY,
       int clientX, int clientY, int button, [bool canBubble, bool cancelable,
       bool ctrlKey, bool altKey, bool shiftKey, bool metaKey,
       EventTarget relatedTarget]);
 
   bool get altKey();
 
   int get button();
 
@@ skipping 18 matching lines @@
   int get screenY();
 
   bool get shiftKey();
 
   Node get toElement();
 
   int get x();
 
   int get y();
 }