Add 'view-mode' class to nodes

Implementing custom view modes is great, but doing so means you can no longer tell what view mode a node is using just by looking at the CSS (like you can with the 'node-teaser' class). I therefore propose adding a 'view-mode' class to nodes (somehow).

I did this myself by overriding template_preprocess_node() in my theme's template.php file:

function THEME_preprocess_node(&$variables) {
  // Add view-mode class to nodes
  $variables['classes_array'][] = drupal_html_class('entity-view-mode--' . $variables['view_mode']);
}

However you'd have to somehow do this in the module itself to include this by default...