just to keep track, a failing test below.

Didn't dig, just verified that not/removing the listener to selectedItem in dispose (as suggested in fix for JDK-8241737) does not make a difference here.

    public static class TabPaneSkin1 extends TabPaneSkin {

        public TabPaneSkin1(TabPane control) {
            super(control);
        }
        
    }
    
    /**
     * memory leak when replacing skin
     */
    @Test
    public void testTabPaneSkin() {
        TabPane control = new TabPane();
        ObservableList<String> data = FXCollections.observableArrayList("Apple", "Orange", "Banana");
        data.forEach(text -> control.getTabs().add(new Tab(text)));
        showControl(control);
        WeakReference<?> weakRef = new WeakReference<>(control.getSkin());
        control.setSkin(new TabPaneSkin1(control));
        attemptGC(weakRef, 10);
        assertNull("skin must be gc'ed", weakRef.get());
    }