Use #attached for block_admin_display_form() instead of drupal_add_css()

Drupal newbie here.
Can you please let me know where in the form tree does the #attached go?
I am trying to add it to the $form['blocks']. Is this right?

  $form['blocks'] = array(
    '#attached' => array(
      'css' => array(drupal_get_path('module', 'block') . '/block.css')
    )
  );

Not sure. I would rather write

  $form['#attached']['css'] = array(
    drupal_get_path('module', 'block') . '/block.css'),
  );

Basically just removing the "blocks" entry, because it needs to be attached to the whole form. Read the Form API reference on api.drupal.org.
You should try to provide a patch for this.

Here's a patch.

Looks good to me.

Committed to 8.x. This is a candidate for backporting to 7.x. I'm moving this to webchick's queue so she can consider committing this to 7.x.

#6: use-attached-for-css-1122584-4.patch queued for re-testing.

This doesn't look like it'll change anything as far as what CSS is shown on the page; merely how it's added.

Committed and pushed to 7.x. Thanks!