Add block context to template_preprocess_menu_attach_block_wrapper()

It would be nice to provide some context to the block when attaching this to the menu.

Our use case is to integrate a custom Block class functionality to the wrapper.

/**
 * Implements template_preprocess_menu_attach_block_wrapper().
 */
function acorn_custom_preprocess_menu_attach_block_wrapper(&$variables) {
  if (isset($variables['block'])) {
    $block = (array) $variables['block'];
    if (!empty($block['css_class'])) {
      $variables['classes_array'][] = drupal_html_class($block['css_class']);
    }
  }
}

But many other possible use cases :)