Remove unnecessary caching

`ActiveSupport::Dependencies.constantize(const_name)` calls
`Reference.new` which is defined as
`ActiveSupport::Dependencies.constantize(const_name)` meaning this call
is already cached and we're doing caching that isn't necessary.

Conflicts:
	actionpack/lib/action_dispatch/routing/route_set.rb

Conflicts:
	actionpack/lib/action_dispatch/routing/route_set.rb

CVE-2015-7581

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -1,6 +1,5 @@
 require 'action_dispatch/journey'
 require 'forwardable'
-require 'thread_safe'
 require 'active_support/concern'
 require 'active_support/core_ext/object/to_query'
 require 'active_support/core_ext/hash/slice'
@@ -24,7 +23,6 @@ class Dispatcher #:nodoc:
         def initialize(options={})
           @defaults = options[:defaults]
           @glob_param = options.delete(:glob)
-          @controller_class_names = ThreadSafe::Cache.new
         end
 
         def call(env)
@@ -74,7 +72,7 @@ def controller(params, default_controller=true)
       private
 
         def controller_reference(controller_param)
-          const_name = @controller_class_names[controller_param] ||= "#{controller_param.camelize}Controller"
+          const_name = "#{controller_param.camelize}Controller"
           ActiveSupport::Dependencies.constantize(const_name)
         end