```ruby
module Turbolinks
  # Corrects the behavior of url_for (and link_to, which uses url_for) with the :back 
  # option by using the X-XHR-Referer request header instead of the standard Referer 
  # request header.
  module XHRUrlFor
    def self.included(base)
      base.alias_method_chain :url_for, :xhr_referer
    end
 
    def url_for_with_xhr_referer(options = {})
      options = (xhr_referer || options) if options == :back
      url_for_without_xhr_referer options
    end

    private
      def xhr_referer
        controller.request.headers["X-XHR-Referer"]
      end
  end
end
```

Remove unnecessary private method extraction because it breaks link_to(:back) in Rails 3
user
```ruby
module Turbolinks
  # Corrects the behavior of url_for (and link_to, which uses url_for) with the :back 
  # option by using the X-XHR-Referer request header instead of the standard Referer 
  # request header.
  module XHRUrlFor
    def self.included(base)
      base.alias_method_chain :url_for, :xhr_referer
    end
 
    def url_for_with_xhr_referer(options = {})
      options = (controller.request.headers["X-XHR-Referer"] || options) if options == :back
      url_for_without_xhr_referer options
    end
  end
end
```
assistant