class ActionDispatch::Flash::FlashHash

def sweep #:nodoc:

:nodoc:
This method is called automatically by filters, so you generally don't need to care about it.

Mark for removal entries that were kept, and delete unkept ones. 
def sweep #:nodoc:
  keys.each do |k|
    unless @used.include?(k)
      @used << k
    else
      delete(k)
      @used.delete(k)
    end
  end
  # clean up after keys that could have been left over by calling reject! or shift on the flash
  (@used - keys).each{ |k| @used.delete(k) }
end