Menus: Improve performance by calling get_privacy_policy_url() once per Walker_Nav_Menu instance rather than for every nav menu item.

The `start_el()` method in `Walker_Nav_Menu` was calling `get_privacy_policy_url()` for every menu item when building menus. This resulted in redundant queries, particularly for menus with many items. This obtains the `get_privacy_policy_url()` value in the constructor for reuse in the `start_el()` method to improve performance.

Redundant code to construct the privacy policy page is also refactored into the `set_up()` method during tests.

Props arzola, swissspidy, westonruter, mukesh27.
Fixes #62818.

Built from https://develop.svn.wordpress.org/trunk@59674


git-svn-id: http://core.svn.wordpress.org/trunk@59017 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-walker-nav-menu.php

@@ -39,6 +39,23 @@ class Walker_Nav_Menu extends Walker {
 		'id'     => 'db_id',
 	);
 
+	/**
+	 * The URL to the privacy policy page.
+	 *
+	 * @since 6.8.0
+	 * @var string
+	 */
+	private $privacy_policy_url;
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 6.8.0
+	 */
+	public function __construct() {
+		$this->privacy_policy_url = get_privacy_policy_url();
+	}
+
 	/**
 	 * Starts the list before the elements are added.
 	 *
@@ -236,7 +253,7 @@ class Walker_Nav_Menu extends Walker {
 		$atts['rel']    = ! empty( $menu_item->xfn ) ? $menu_item->xfn : '';
 
 		if ( ! empty( $menu_item->url ) ) {
-			if ( get_privacy_policy_url() === $menu_item->url ) {
+			if ( $this->privacy_policy_url === $menu_item->url ) {
 				$atts['rel'] = empty( $atts['rel'] ) ? 'privacy-policy' : $atts['rel'] . ' privacy-policy';
 			}
 

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.8-alpha-59673';
+$wp_version = '6.8-alpha-59674';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.