Don't deprecate to_prepare.

actionpack/lib/action_dispatch/middleware/callbacks.rb

+require 'active_support/core_ext/module/delegation'
+
 module ActionDispatch
   # Provide callbacks to be executed before and after the request dispatch.
   class Callbacks
@@ -5,10 +7,8 @@ class Callbacks
 
     define_callbacks :call, :rescuable => true
 
-    def self.to_prepare(*args, &block)
-      ActiveSupport::Deprecation.warn "ActionDispatch::Callbacks.to_prepare is deprecated. " <<
-        "Please use ActionDispatch::Reloader.to_prepare instead."
-      ActionDispatch::Reloader.to_prepare(*args, &block)
+    class << self
+      delegate :to_prepare, :to_cleanup, :to => "ActionDispatch::Reloader"
     end
 
     def self.before(*args, &block)

actionpack/test/dispatch/callbacks_test.rb

@@ -29,14 +29,16 @@ def test_before_and_after_callbacks
     assert_equal 4, Foo.b
   end
 
-  def test_to_prepare_deprecation
-    prepared = false
-    assert_deprecated do
-      ActionDispatch::Callbacks.to_prepare { prepared = true }
-    end
+  def test_to_prepare_and_cleanup_delegation
+    prepared = cleaned = false
+    ActionDispatch::Callbacks.to_prepare { prepared = true }
+    ActionDispatch::Callbacks.to_prepare { cleaned = true }
 
     ActionDispatch::Reloader.prepare!
     assert prepared
+
+    ActionDispatch::Reloader.cleanup!
+    assert cleaned
   end
 
   private