class ActionDispatch::FileHandler

def gzip_file_path(path)
  can_gzip_mime = content_type(path) =~ /\A(?:text\/|application\/javascript)/
  gzip_path     = "#{path}.gz"
  if can_gzip_mime && File.exist?(File.join(@root, ::Rack::Utils.unescape_path(gzip_path)))
    gzip_path
  else
    false
  end
end