Change pre_render, post_render, and after_build callbacks to accept callables

Works for me :)

We need this to finish #1982138: Clean out field_ui.admin.inc

+1 for this, of course.

But more generally, rather than keeping with one-off "this callback" and "oh, this one too" patches, it might be a good idea to check all remaining render and form callbacks and make sure they consistently accept callables ?

It seems the only remaining one is #after_build, let's just finish this off right.

Beautiful, thanks!

+++ b/core/includes/form.incundefined
@@ -1939,8 +1939,8 @@ function form_builder($form_id, &$element, &$form_state) {
+      $element = call_user_func($callable, $element, $form_state);

Apparently this will need to be call_user_func_array()? call_user_func() doesn't work with references

Just in general: do we have to convert all of them to cufa?

+++ b/core/modules/system/system.api.phpundefined
@@ -282,7 +282,7 @@ function hook_queue_info_alter(&$queues) {
- *  - "#pre_render": array of callback functions taking $element and $form_state.
+ *  - "#pre_render": array of callables taking $element and $form_state.

Let's also change after_build, post_render

I looked into it, those docs are wrong.
And this is what was needed for the references to work. cufa is exempt from the call time pass-by-reference rules.

Ok we should be good now. Docs and code look good.

Committed 523d64a and pushed to 8.x. Thanks!