#action_view/helpers/asset_tag_helper.rb
class AssetTag

   # NOTE:  This 'Cache' stays around forever
   Cache = {}
   CacheGuard = Mutex.new

   def self.create(template, controller, source, include_host = true)
      CacheGuard.synchronize do
          key = if controller.respond_to?(:request)
            [self, controller.request.protocol,
            ActionController::Base.asset_host,
            ActionController::Base.relative_url_root,
            source, include_host]
           else
             [self, ActionController::Base.asset_host, source, include_host]
           end

           # NOTE Put EVERY asset tag (css,js, and all images) into a static cache
           Cache[key] ||= new(template, controller, source, include_host).freeze
         end
     end