Post List Table: Ensure that edit.php with no query string produces the proper markup and links in the date column header.

Add 2 methods to `WP_List_Table`, `->get_orderby()` and `->get_order()`. Override the methods in `WP_Posts_List_Table`.

`WP_Posts_List_Table` calls `wp_edit_posts_query()` in `->prepare_items()` which is a wrapper for `wp()`. As such, we can obtain `orderby` and `order` via `get_query_var()`, instead of the URL.

Fixes #25493.



git-svn-id: https://develop.svn.wordpress.org/trunk@34728 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/class-wp-posts-list-table.php

@@ -120,6 +120,30 @@ class WP_Posts_List_Table extends WP_List_Table {
 		return current_user_can( get_post_type_object( $this->screen->post_type )->cap->edit_posts );
 	}
 
+	/**
+	 * Get the value of the 'orderby' query var.
+	 *
+	 * @access protected
+	 * @since 4.4.0
+	 *
+	 * @return string The value of 'orderby'.
+	 */
+	protected function get_orderby() {
+		return strtolower( get_query_var( 'orderby' ) );
+	}
+
+	/**
+	 * Get the value of the 'order' query var.
+	 *
+	 * @access protected
+	 * @since 4.4.0
+	 *
+	 * @return string The value of 'order'.
+	 */
+	protected function get_order() {
+		return strtolower( get_query_var( 'order' ) );
+	}
+
 	/**
 	 *
 	 * @global array    $avail_post_stati
@@ -130,6 +154,7 @@ class WP_Posts_List_Table extends WP_List_Table {
 	public function prepare_items() {
 		global $avail_post_stati, $wp_query, $per_page, $mode;
 
+		// is going to call wp()
 		$avail_post_stati = wp_edit_posts_query();
 
 		$this->set_hierarchical_display( is_post_type_hierarchical( $this->screen->post_type ) && 'menu_order title' === $wp_query->query['orderby'] );