Remove usage of memoizable from ActionPack.

actionpack/lib/action_dispatch/http/headers.rb

@@ -3,9 +3,10 @@
 module ActionDispatch
   module Http
     class Headers < ::Hash
-      extend ActiveSupport::Memoizable
+      @@env_cache = Hash.new { |h,k| h[k] = "HTTP_#{k.upcase.gsub(/-/, '_')}" }
 
       def initialize(*args)
+
         if args.size == 1 && args[0].is_a?(Hash)
           super()
           update(args[0])
@@ -25,9 +26,8 @@ def [](header_name)
       private
         # Converts a HTTP header name to an environment variable name.
         def env_name(header_name)
-          "HTTP_#{header_name.upcase.gsub(/-/, '_')}"
+          @@env_cache[header_name]
         end
-        memoize :env_name
     end
   end
 end

actionpack/lib/action_view/helpers/date_helper.rb

@@ -621,7 +621,6 @@ def time_tag(date_or_time, *args)
     end
 
     class DateTimeSelector #:nodoc:
-      extend ActiveSupport::Memoizable
       include ActionView::Helpers::TagHelper
 
       DEFAULT_PREFIX = 'date'.freeze
@@ -786,11 +785,12 @@ def select_year
         # Returns translated month names, but also ensures that a custom month
         # name array has a leading nil element.
         def month_names
-          month_names = @options[:use_month_names] || translated_month_names
-          month_names.unshift(nil) if month_names.size < 13
-          month_names
+          @month_names ||= begin
+            month_names = @options[:use_month_names] || translated_month_names
+            month_names.unshift(nil) if month_names.size < 13
+            month_names
+          end
         end
-        memoize :month_names
 
         # Returns translated month names.
         #  => [nil, "January", "February", "March",
@@ -825,9 +825,8 @@ def month_name(number)
         end
 
         def date_order
-          @options[:order] || translated_date_order
+          @date_order ||= @options[:order] || translated_date_order
         end
-        memoize :date_order
 
         def translated_date_order
           I18n.translate(:'date.order', :locale => @options[:locale]) || []