Don't use action_controller.perform_caching to enable rack-rack.

Setting the action_dispatch.rack_cache options to true or a hash should
be the way to enable it.

railties/lib/rails/application.rb

@@ -286,7 +286,7 @@ def reload_dependencies? #:nodoc:
     def default_middleware_stack #:nodoc:
       ActionDispatch::MiddlewareStack.new.tap do |middleware|
         app = self
-        if rack_cache = config.action_controller.perform_caching && config.action_dispatch.rack_cache
+        if rack_cache = config.action_dispatch.rack_cache
           begin
             require 'rack/cache'
           rescue LoadError => error

railties/test/application/middleware/cache_test.rb

@@ -49,8 +49,6 @@ def render_conditionally(headers)
           get ':controller(/:action)'
         end
       RUBY
-
-      add_to_config "config.action_dispatch.rack_cache = true"
     end
 
     def test_cache_keeps_if_modified_since
@@ -80,6 +78,8 @@ def test_cache_is_disabled_in_dev_mode
     def test_cache_works_with_expires
       simple_controller
 
+      add_to_config "config.action_dispatch.rack_cache = true"
+
       get "/expires/expires_header"
       assert_equal "miss, store",        last_response.headers["X-Rack-Cache"]
       assert_equal "max-age=10, public", last_response.headers["Cache-Control"]
@@ -96,6 +96,8 @@ def test_cache_works_with_expires
     def test_cache_works_with_expires_private
       simple_controller
 
+      add_to_config "config.action_dispatch.rack_cache = true"
+
       get "/expires/expires_header", private: true
       assert_equal "miss",                last_response.headers["X-Rack-Cache"]
       assert_equal "private, max-age=10", last_response.headers["Cache-Control"]
@@ -110,6 +112,8 @@ def test_cache_works_with_expires_private
     def test_cache_works_with_etags
       simple_controller
 
+      add_to_config "config.action_dispatch.rack_cache = true"
+
       get "/expires/expires_etag"
       assert_equal "miss, store", last_response.headers["X-Rack-Cache"]
       assert_equal "public",      last_response.headers["Cache-Control"]
@@ -125,6 +129,8 @@ def test_cache_works_with_etags
     def test_cache_works_with_etags_private
       simple_controller
 
+      add_to_config "config.action_dispatch.rack_cache = true"
+
       get "/expires/expires_etag", private: true
       assert_equal "miss",                                last_response.headers["X-Rack-Cache"]
       assert_equal "must-revalidate, private, max-age=0", last_response.headers["Cache-Control"]
@@ -140,6 +146,8 @@ def test_cache_works_with_etags_private
     def test_cache_works_with_last_modified
       simple_controller
 
+      add_to_config "config.action_dispatch.rack_cache = true"
+
       get "/expires/expires_last_modified"
       assert_equal "miss, store", last_response.headers["X-Rack-Cache"]
       assert_equal "public",      last_response.headers["Cache-Control"]
@@ -155,6 +163,8 @@ def test_cache_works_with_last_modified
     def test_cache_works_with_last_modified_private
       simple_controller
 
+      add_to_config "config.action_dispatch.rack_cache = true"
+
       get "/expires/expires_last_modified", private: true
       assert_equal "miss",                                last_response.headers["X-Rack-Cache"]
       assert_equal "must-revalidate, private, max-age=0", last_response.headers["Cache-Control"]

railties/test/application/middleware_test.rb

@@ -57,15 +57,12 @@ def app
     end
 
     test "Rack::Cache is not included by default" do
-      add_to_config "config.action_controller.perform_caching = true"
-
       boot!
 
       assert !middleware.include?("Rack::Cache"), "Rack::Cache is not included in the default stack unless you set config.action_dispatch.rack_cache"
     end
 
-    test "Rack::Cache is present when action_controller.perform_caching is set and action_dispatch.rack_cache is set" do
-      add_to_config "config.action_controller.perform_caching = true"
+    test "Rack::Cache is present when action_dispatch.rack_cache is set" do
       add_to_config "config.action_dispatch.rack_cache = true"
 
       boot!