Ticket #28835: 28835_4.patch

src/wp-admin/js/customize-widgets.js

@@ -316 +316 @@
                                 isEsc = ( event.which === 27 ),
                                 isDown = ( event.which === 40 ),
                                 isUp = ( event.which === 38 ),
+                                isTab = ( event.which === 9 ),
+                                isShift = ( event.shiftKey ),
                                 selected = null,
                                 firstVisible = this.$el.find( '> .widget-tpl:visible:first' ),
                                 lastVisible = this.$el.find( '> .widget-tpl:visible:last' ),
+                                isLastWidgetFocused =  $( event.target ).is( '.widget-tpl:visible:last' ),
                                 isSearchFocused = $( event.target ).is( this.$search );
 
                         if ( isDown || isUp ) {
@@ -357 +360 @@
                         } else if ( isEsc ) {
                                 this.close( { returnFocus: true } );
                         }
+                        
+                        if ( isTab ) {
+                                if( isShift ) {
+                                        if ( isSearchFocused ) {
+                                                $( '.control-section:has(.open) .add-new-widget' ).focus();
+                                                event.preventDefault();
                 }
+                                } else {
+                                        if ( isLastWidgetFocused ) {
+                                                $( '.control-section:has(.open) .add-new-widget' ).focus();
+                                                event.preventDefault();
+                                        }
+                                }
+                        }
+                }
         });
 
         /**