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

client/html/src/WheelEvent.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 WheelEvent extends UIEvent factory WheelEventWrappingImplementation {
+interface WheelEvent extends UIEvent default WheelEventWrappingImplementation {
 
   WheelEvent(int deltaX, int deltaY, Window view, int screenX, int screenY,
       int clientX, int clientY, [bool ctrlKey, bool altKey, bool shiftKey,
       bool metaKey]);
 
   bool get altKey();
 
   int get clientX();
 
   int get clientY();
@@ skipping 15 matching lines @@
   int get wheelDelta();
 
   int get wheelDeltaX();
 
   int get wheelDeltaY();
 
   int get x();
 
   int get y();
 }