Phase out local storage usage in PortSync code

client/dart.js

Index: client/dart.js
diff --git a/client/dart.js b/client/dart.js
index c76e3fa5fad0d02620f7b0050b640179aa8c314a..1c8b333be70329f766432575e8955014a55d83ae 100644
--- a/client/dart.js
+++ b/client/dart.js
@@ -159,11 +159,21 @@ function ReceivePortSync() {
 
   window.registerPort = function(name, port) {
     var stringified = JSON.stringify(serialize(port));
-    window.localStorage['dart-port:' + name] = stringified;
+    var attrName = 'dart-port:' + name;
+    document.documentElement.setAttribute(attrName, stringified);
+    // TODO(vsm): Phase out usage of localStorage.  We're leaving it in
+    // temporarily for backwards compatibility.
+    window.localStorage[attrName] = stringified;
   };
 
   window.lookupPort = function(name) {
-    var stringified = window.localStorage['dart-port:' + name];
+    var attrName = 'dart-port:' + name;
+    var stringified = document.documentElement.getAttribute(attrName);
+    // TODO(vsm): Phase out usage of localStorage.  We're leaving it in
+    // temporarily for backwards compatibility.
+    if (!stringified) {
+      stringified = window.localStorage[attrName];
+    }
     return deserialize(JSON.parse(stringified));
   };