just return path parameters

actionpack/lib/action_dispatch/http/parameters.rb

@@ -24,14 +24,13 @@ module ActionDispatch
       alias :params :parameters
 
       def path_parameters=(parameters) #:nodoc:
-        @symbolized_path_params = nil
         @env.delete('action_dispatch.request.parameters')
         @env[Routing::RouteSet::PARAMETERS_KEY] = parameters
       end
 
       # The same as <tt>path_parameters</tt> with explicitly symbolized keys.
       def symbolized_path_parameters
-        @symbolized_path_params ||= path_parameters.symbolize_keys
+        path_parameters
       end
 
       # Returns a hash with the \parameters used to form the \path of the request.