Move all files to 2017/

2017/web/core/modules/system/system.api.php

@@ -0,0 +1,38 @@
+<?php
+
+/**
+ * @file
+ * Hooks provided by the System module.
+ */
+
+use Drupal\Core\Url;
+
+/**
+ * @addtogroup hooks
+ * @{
+ */
+
+/**
+ * Alters theme operation links.
+ *
+ * @param $theme_groups
+ *   An associative array containing groups of themes.
+ *
+ * @see system_themes_page()
+ */
+function hook_system_themes_page_alter(&$theme_groups) {
+  foreach ($theme_groups as $state => &$group) {
+    foreach ($theme_groups[$state] as &$theme) {
+      // Add a foo link to each list of theme operations.
+      $theme->operations[] = [
+        'title' => t('Foo'),
+        'url' => Url::fromRoute('system.themes_page'),
+        'query' => ['theme' => $theme->getName()],
+      ];
+    }
+  }
+}
+
+/**
+ * @} End of "addtogroup hooks".
+ */