Adding 'part of html' to all files which are used by dart:html.

sdk/lib/html/src/CrossFrameTypes.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.
 
+part of html;
+
 abstract class Window {
   // Fields.
   Location get location;
   History get history;
 
   bool get closed;
   Window get opener;
   Window get parent;
   Window get top;
 
   // Methods.
   void focus();
   void blur();
   void close();
   void postMessage(var message, String targetOrigin, [List messagePorts = null]);
 }
 
 abstract class Location {
   void set href(String val);
 }
 
 abstract class History {
   void back();
   void forward();
   void go(int distance);
 }