Ensure params wrapper settings are not inherited and calculated each time.

actionpack/lib/action_controller/metal/params_wrapper.rb

@@ -125,7 +125,7 @@ module ActionController
       # module is inherited.
       def inherited(klass)
         if klass._wrapper_options[:format].present?
-          klass._set_wrapper_defaults(klass._wrapper_options)
+          klass._set_wrapper_defaults(klass._wrapper_options.slice(:format))
         end
         super
       end

railties/test/application/configuration_test.rb

@@ -12,7 +12,6 @@ end
 
 class ::MyOtherMailObserver < ::MyMailObserver; end
 
-
 module ApplicationTests
   class ConfigurationTest < Test::Unit::TestCase
     include ActiveSupport::Testing::Isolation
@@ -437,10 +436,35 @@ module ApplicationTests
       app_file 'config/initializers/wrap_parameters.rb', <<-RUBY
         ActionController::Base.wrap_parameters :format => [:json]
       RUBY
-      require "#{app_path}/config/environment"
-      require 'action_controller/base'
 
-      assert_equal [:json], ActionController::Base._wrapper_options[:format]
+      app_file 'app/models/post.rb', <<-RUBY
+      class Post
+        def self.column_names
+          %w(title)
+        end
+      end
+      RUBY
+
+      app_file 'app/controllers/posts_controller.rb', <<-RUBY
+      class PostsController < ApplicationController
+        def index
+          render :text => params[:post].inspect
+        end
+      end
+      RUBY
+
+      add_to_config <<-RUBY
+        routes.append do
+          resources :posts
+        end
+      RUBY
+
+      require "#{app_path}/config/environment"
+      require "rack/test"
+      extend Rack::Test::Methods
+
+      post "/posts.json", '{ "title": "foo", "name": "bar" }', "CONTENT_TYPE" => "application/json"
+      assert_equal '{"title"=>"foo"}', last_response.body
     end
 
     test "config.action_dispatch.ignore_accept_header" do