MDL-28168 Improved custom_menu constructor

This improves custom_menu constructor by dropping support for useless
$text parameter and replacing it with the menu definition. This makes
custom_menu instance independent on the place where the menu is defined
($CFG->custommenuitems) and can be unit-tested. Also, multiple instances
of custom_menu can be instantiated now which can be interesting in the
future.

lib/outputcomponents.php

@@ -2323,15 +2323,17 @@ class custom_menu_item implements renderable {
  * @since     Moodle 2.0
  */
 class custom_menu extends custom_menu_item {
+
     /**
      * Creates the custom menu
-     * @param string $text Sets the text for this custom menu, never gets used and is optional
+     *
+     * @param string $definition the menu items definition in syntax required by {@link convert_text_to_menu_nodes()}
      */
-    public function __construct($text='base') {
-        global $CFG;
-        parent::__construct($text);
-        if (!empty($CFG->custommenuitems)) {
-            $this->override_children(self::convert_text_to_menu_nodes($CFG->custommenuitems));
+    public function __construct($definition = '') {
+
+        parent::__construct('root'); // create virtual root element of the menu
+        if (!empty($definition)) {
+            $this->override_children(self::convert_text_to_menu_nodes($definition));
         }
     }
 

lib/outputrenderers.php

@@ -2410,7 +2410,7 @@ EOD;
         if (empty($CFG->custommenuitems)) {
             return '';
         }
-        $custommenu = new custom_menu();
+        $custommenu = new custom_menu($CFG->custommenuitems);
         return $this->render_custom_menu($custommenu);
     }