Move content length to the server, this brings the same behavior as in rack 1.2.

railties/lib/rails/application.rb

@@ -141,8 +141,6 @@ def config
 
     def default_middleware_stack
       ActionDispatch::MiddlewareStack.new.tap do |middleware|
-        middleware.use ::Rails::Rack::ContentLength, config.action_dispatch.x_sendfile_header
-
         if rack_cache = config.action_controller.perform_caching && config.action_dispatch.rack_cache
           require "action_dispatch/http/rack_cache"
           middleware.use ::Rack::Cache, rack_cache

railties/lib/rails/commands/server.rb

@@ -78,6 +78,7 @@ def middleware
       middlewares = []
       middlewares << [Rails::Rack::LogTailer, log_path] unless options[:daemonize]
       middlewares << [Rails::Rack::Debugger]  if options[:debugger]
+      middlewares << [Rails::Rack::ContentLength]
       Hash.new(middlewares)
     end
 

railties/test/application/middleware_test.rb

@@ -19,7 +19,6 @@ def app
       boot!
 
       assert_equal [
-        "Rails::Rack::ContentLength",
         "ActionDispatch::Static",
         "Rack::Lock",
         "ActiveSupport::Cache::Strategy::LocalCache",
@@ -49,7 +48,7 @@ def app
 
       boot!
 
-      assert_equal "Rack::Cache", middleware.second
+      assert_equal "Rack::Cache", middleware.first
     end
 
     test "Rack::SSL is present when force_ssl is set" do
@@ -104,7 +103,7 @@ def app
     end
 
     test "insert middleware after" do
-      add_to_config "config.middleware.insert_after Rails::Rack::ContentLength, Rack::Config"
+      add_to_config "config.middleware.insert_after ActionDispatch::Static, Rack::Config"
       boot!
       assert_equal "Rack::Config", middleware.second
     end
@@ -112,12 +111,12 @@ def app
     test "RAILS_CACHE does not respond to middleware" do
       add_to_config "config.cache_store = :memory_store"
       boot!
-      assert_equal "Rack::Runtime", middleware.fourth
+      assert_equal "Rack::Runtime", middleware.third
     end
 
     test "RAILS_CACHE does respond to middleware" do
       boot!
-      assert_equal "Rack::Runtime", middleware.fifth
+      assert_equal "Rack::Runtime", middleware.fourth
     end
 
     test "identity map is inserted" do
@@ -127,7 +126,7 @@ def app
     end
 
     test "insert middleware before" do
-      add_to_config "config.middleware.insert_before Rails::Rack::ContentLength, Rack::Config"
+      add_to_config "config.middleware.insert_before ActionDispatch::Static, Rack::Config"
       boot!
       assert_equal "Rack::Config", middleware.first
     end
@@ -201,4 +200,4 @@ def middleware
         AppTemplate::Application.middleware.map(&:klass).map(&:name)
       end
   end
-end
+end