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

sdk/lib/html/templates/html/dart2js/impl_LocalWindow.darttemplate

 // 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;
+
 class $CLASSNAME$EXTENDS$IMPLEMENTS native "@*DOMWindow" {
 
   Document get document => JS('Document', '#.document', this);
 
   Window _open2(url, name) => JS('Window', '#.open(#,#)', this, url, name);
 
   Window _open3(url, name, options) =>
       JS('Window', '#.open(#,#,#)', this, url, name, options);
 
   Window open(String url, String name, [String options]) {
@@ skipping 123 matching lines @@
    * port may be retrieved by any isolate (or JavaScript script)
    * running in this window.
    */
   void registerPort(String name, var port) {
     var serialized = _serialize(port);
     localStorage['dart-port:$name'] = JSON.stringify(serialized);
   }
 
 $!MEMBERS
 }