Avoid leak into controller's action_methods

actionpack/lib/abstract_controller/layouts.rb

@@ -309,6 +309,7 @@ def _write_layout_method # :nodoc:
             RUBY
           when Proc
             define_method :_layout_from_proc, &_layout
+            protected :_layout_from_proc
             <<-RUBY
               result = _layout_from_proc(#{_layout.arity == 0 ? '' : 'self'})
               return #{default_behavior} if result.nil?

actionpack/test/abstract/layouts_test.rb

@@ -8,6 +8,8 @@ class Base < AbstractController::Base
       include AbstractController::Rendering
       include AbstractController::Layouts
 
+      abstract!
+
       self.view_paths = [ActionView::FixtureResolver.new(
         "layouts/hello.erb"             => "With String <%= yield %>",
         "layouts/hello_override.erb"    => "With Override <%= yield %>",
@@ -251,6 +253,10 @@ class TestBase < ActiveSupport::TestCase
         assert_equal "Hello nil!", controller.response_body
       end
 
+      test "when layout is specified as a proc, do not leak any methods into controller's action_methods" do
+        assert_equal Set.new(['index']), WithProc.action_methods
+      end
+
       test "when layout is specified as a proc, call it and use the layout returned" do
         controller = WithProc.new
         controller.process(:index)