Defer loading action_controller

Use the lazy-load hooks to include ::SecureHeaders. This will prevent action_controller/action_view from getting loaded unless it's required.

lib/secure_headers/railtie.rb

@@ -3,7 +3,11 @@ if defined?(Rails::Railtie)
   module SecureHeaders
     class Railtie < Rails::Engine
       isolate_namespace ::SecureHeaders if defined? isolate_namespace # rails 3.0
-      ActionController::Base.send :include, ::SecureHeaders
+      initializer "secure_headers.action_controller" do
+        ActiveSupport.on_load(:action_controller) do
+          include ::SecureHeaders
+        end
+      end
     end
   end
 else
@@ -34,4 +38,4 @@ else
   if defined? ActionController::Routing
     ActionController::Routing::RouteSet::Mapper.send :include, ::SecureHeaders::Routing::MapperExtensions
   end
-end
+end