Issue #6205: Provide class names to operations links on Appearance page.

By @laryn and @bugfolder.

core/modules/system/system.admin.inc

@@ -158,21 +158,21 @@ function system_themes_page() {
       // Create the operations links.
       $query['theme'] = $theme->name;
       if (backdrop_theme_access($theme) && theme_has_settings($theme->name)) {
-        $theme->operations[] = array(
+        $theme->operations['settings'] = array(
           'title' => t('Settings'),
           'href' => 'admin/appearance/settings/' . $theme->name,
           'attributes' => array('title' => t('Settings for !theme theme', array('!theme' => $theme->info['name']))),
         );
       }
       if (!empty($theme->status)) {
         if (!$theme->is_default) {
-          $theme->operations[] = array(
+          $theme->operations['disable'] = array(
             'title' => t('Disable'),
             'href' => 'admin/appearance/disable',
             'query' => $query,
             'attributes' => array('title' => t('Disable !theme theme', array('!theme' => $theme->info['name']))),
           );
-          $theme->operations[] = array(
+          $theme->operations['default'] = array(
             'title' => t('Set default'),
             'href' => 'admin/appearance/default',
             'query' => $query,
@@ -181,13 +181,13 @@ function system_themes_page() {
         }
       }
       else {
-        $theme->operations[] = array(
+        $theme->operations['enable'] = array(
           'title' => t('Enable'),
           'href' => 'admin/appearance/enable',
           'query' => $query,
           'attributes' => array('title' => t('Enable !theme theme', array('!theme' => $theme->info['name']))),
         );
-        $theme->operations[] = array(
+        $theme->operations['enable-default'] = array(
           'title' => t('Enable and set default'),
           'href' => 'admin/appearance/default',
           'query' => $query,