Index: src/wp-includes/script-loader.php
===================================================================
--- src/wp-includes/script-loader.php	(revision 47352)
+++ src/wp-includes/script-loader.php	(working copy)
@@ -1359,9 +1359,10 @@
 				'wpWidgets.l10n = %s;',
 				wp_json_encode(
 					array(
-						'save'      => __( 'Save' ),
-						'saved'     => __( 'Saved' ),
-						'saveAlert' => __( 'The changes you made will be lost if you navigate away from this page.' ),
+						'save'        => __( 'Save' ),
+						'saved'       => __( 'Saved' ),
+						'saveAlert'   => __( 'The changes you made will be lost if you navigate away from this page.' ),
+						'widgetAdded' => __( 'Widget has been added to the selected sidebar' ),
 					)
 				)
 			)