form_alter path-checking issues on boxes with ajax-y media form elements

I have a couple box implementations that include custom Media form elements (image and video fields) inside custom Boxes.

In the process of upgrading Media to the latest 7.x-2.x-dev (7.x-2.0-beta1+9-dev) and Boxes to 7.x-1.2 (as well as a whole lot of other modules...) the boxes were no longer saving my chosen media items.

I tracked the problem down to the fact that the $form was losing boxes' submit handler, 'boxes_box_form_submit', when I would use (change the value in) the media form element.

It looks like when the media element does its ajax stuff, the arg() path is no longer set to 'admin/structure/block/manage/boxes' (which boxes_form_alter() checks for) but is instead 'media/ajax/settings/options/FORM_ELEMENT' (where FORM_ELEMENT is the ID of my media form element).

So, when the form is saved, the boxes submit handler is not called (and therefore neither is my custom my_box_box->options_submit()).

I was able to fix this by, in boxes_form_alter(), testing $form['#action'] instead of the path:

-  if (($form_id != 'block_admin_configure' || $path != 'admin/structure/block/manage/boxes') &&
+  if (($form_id != 'block_admin_configure' || strpos($form['#action'], '/admin/structure/block/manage/boxes') != 0) &&

While this is working for me now, I don't actually know:

1. Where/when this change in operation originated.
2. Whether Media is doing things properly and it's ok that the arg() path is being changed.
3. Whether it's always safe and effective for Boxes to rely on $form['action'].

Patch forthcoming.