`WP_Theme` has an ad hoc property in `WP_MS_Themes_List_Table`, `$update`. This can be set to a default value on the class, as it's not obtained via `__get()`.

See #33491.


git-svn-id: https://develop.svn.wordpress.org/trunk@33957 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-theme.php

@@ -4,9 +4,18 @@
  *
  * @package WordPress
  * @subpackage Theme
+ * @since 3.4.0
  */
-
 final class WP_Theme implements ArrayAccess {
+	/**
+	 * Whether the theme has been marked as updateable
+	 *
+	 * @see WP_MS_Themes_List_Table
+	 *
+	 * @access public
+	 * @var bool
+	 */
+	public $update = false;
 
 	/**
 	 * Headers for style.css files.