Combobox does not select an item when appended to DOM, but before 'items' are set

[asashour]

Description

vaadin-combo-box does not select an item when appended to DOM, but before items are set (Chrome)

Expected outcome

A combox should always select 'item1', no matter what order the appendChild()/.items/.selectedItem is set

Actual outcome

In latest Chrome, the first scenario appendThenSelectedThenItems() doesn't show selected value, but in FF ESR, it does.

Live Demo

https://jsfiddle.net/v6mqmcwj/1/

Steps to reproduce

1. Open the page in a web browser.
2. Click on four buttons
3. Check the added comboboxes

Browsers Affected

• Chrome
• Firefox (works)
• Safari (not tested)
• Edge (not tested)
• IE 11 (doesn't show the combobox at all)
• iOS Safari (not tested)
• Android Chrome (not tested)

[asashour]

Can someone please confirm if this is a bug, or an expected behavior, before trying to fix it?