How to make Rails 3 set cookies on the top-level domain, so that I can have a cookie-free subdomain for assets?
===

I'm trying to set cookies only under my top-level domain "dingyu.me", so that my subdomain "assets.dingyu.me" is cookie-free.

This is what I have tried in `session_store.rb`:
  
    domain = Rails.env.production? ? "dingyu.me" : nil
    LonelyThinker::Application.config.session_store :cookie_store, key: 'mykey', domain: domain

Unfortunately, however, Rails still set cookies on my subdomain "assets.dingyu.me". How should I do it?

Thanks!