Phase out local storage usage in PortSync code

sdk/lib/html/dart2js/html_dart2js.dart

 library html;
 
 import 'dart:isolate';
 import 'dart:json';
 import 'dart:svg' as svg;
 // 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.
 
 // DO NOT EDIT
@@ skipping 11983 matching lines @@
   IDBFactory get indexedDB() =>
       JS('IDBFactory',
          '#.indexedDB || #.webkitIndexedDB || #.mozIndexedDB',
          this, this, this);
 
   /**
    * Lookup a port by its [name].  Return null if no port is
    * registered under [name].
    */
   SendPortSync lookupPort(String name) {
-    var port = JSON.parse(localStorage['dart-port:$name']);
+    var port = JSON.parse(document.documentElement.attributes['dart-port:$name']);
     return _deserialize(port);
   }
 
   /**
    * Register a [port] on this window under the given [name].  This
    * 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:$name'] = JSON.stringify(serialized);
+    document.documentElement.attributes['dart-port:$name'] = JSON.stringify(serialized);
   }
 
 
   /**
    * @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent
    */
   LocalWindowEvents get on =>
     new LocalWindowEvents(this);
 
   static const int PERSISTENT = 1;
@@ skipping 13038 matching lines @@
     if (length < 0) throw new ArgumentError('length');
     if (start < 0) throw new RangeError.value(start);
     int end = start + length;
     if (end > a.length) throw new RangeError.value(end);
     for (int i = start; i < end; i++) {
       accumulator.add(a[i]);
     }
     return accumulator;
   }
 }