Type 'com.google.gwt.user.client.Doesn't matter either Chrome or Firefox I am using.
rpc.XsrfToken' was not assignable to 'com.google.gwt.user.client. rpc.IsSerializable' and did not have a custom field serializer. For security purposes, this type will not be deserialized.
Deleting cookies and temp files does not help either.
Open another new post, then Copy & paste to the new post seems working.