diff --git a/src/wp-admin/includes/class-bulk-plugin-upgrader-skin.php b/src/wp-admin/includes/class-bulk-plugin-upgrader-skin.php
index 9844e19460..7cbf334ee2 100644
--- a/src/wp-admin/includes/class-bulk-plugin-upgrader-skin.php
+++ b/src/wp-admin/includes/class-bulk-plugin-upgrader-skin.php
@@ -16,7 +16,16 @@
  * @see Bulk_Upgrader_Skin
  */
 class Bulk_Plugin_Upgrader_Skin extends Bulk_Upgrader_Skin {
-	public $plugin_info = array(); // Plugin_Upgrader::bulk_upgrade() will fill this in.
+
+	/**
+	 * Plugin info.
+	 *
+	 * The Plugin_Upgrader::bulk_upgrade() method will fill this in
+	 * with info retrieved from the get_plugin_data() function.
+	 *
+	 * @var array Plugin data. Values will be empty if not supplied by the plugin.
+	 */
+	public $plugin_info = array();
 
 	public function add_strings() {
 		parent::add_strings();
diff --git a/src/wp-admin/includes/class-bulk-theme-upgrader-skin.php b/src/wp-admin/includes/class-bulk-theme-upgrader-skin.php
index 94daa27131..8ec3bbf5f5 100644
--- a/src/wp-admin/includes/class-bulk-theme-upgrader-skin.php
+++ b/src/wp-admin/includes/class-bulk-theme-upgrader-skin.php
@@ -16,7 +16,17 @@
  * @see Bulk_Upgrader_Skin
  */
 class Bulk_Theme_Upgrader_Skin extends Bulk_Upgrader_Skin {
-	public $theme_info = array(); // Theme_Upgrader::bulk_upgrade() will fill this in.
+
+	/**
+	 * Theme info.
+	 *
+	 * The Theme_Upgrader::bulk_upgrade() method will fill this in
+	 * with info retrieved from the Theme_Upgrader::theme_info() method,
+	 * which in turn calls the wp_get_theme() function.
+	 *
+	 * @var WP_Theme|false The theme's info object, or false.
+	 */
+	public $theme_info = false;
 
 	public function add_strings() {
 		parent::add_strings();
diff --git a/src/wp-admin/includes/class-wp-ajax-upgrader-skin.php b/src/wp-admin/includes/class-wp-ajax-upgrader-skin.php
index bb5a961251..a3b2f9aaef 100644
--- a/src/wp-admin/includes/class-wp-ajax-upgrader-skin.php
+++ b/src/wp-admin/includes/class-wp-ajax-upgrader-skin.php
@@ -18,6 +18,27 @@
  */
 class WP_Ajax_Upgrader_Skin extends Automatic_Upgrader_Skin {
 
+	/**
+	 * Plugin info.
+	 *
+	 * The Plugin_Upgrader::bulk_upgrade() method will fill this in
+	 * with info retrieved from the get_plugin_data() function.
+	 *
+	 * @var array Plugin data. Values will be empty if not supplied by the plugin.
+	 */
+	public $plugin_info = array();
+
+	/**
+	 * Theme info.
+	 *
+	 * The Theme_Upgrader::bulk_upgrade() method will fill this in
+	 * with info retrieved from the Theme_Upgrader::theme_info() method,
+	 * which in turn calls the wp_get_theme() function.
+	 *
+	 * @var WP_Theme|false The theme's info object, or false.
+	 */
+	public $theme_info = false;
+
 	/**
 	 * Holds the WP_Error object.
 	 *