Incorrect handling of multiple font-sizes chosen at the same time

[Piotrek Koszuliński]

Tested on Firefox and Chrome.

1. Open any sample.
2. Place caret in the editor.
3. Choose font size 20.
4. Type few letters.
5. Choose font size 28.
6. Type few letters.
7. Choose font size 28 again so it will be removed.
8. Type few letters.
9. Typed letters has font size 20, but 28 is still highlighted.
10. Open combo again - 28 is highlighted.
11. Click 20.
12. Everything is ok now - size in combo and for typed text is back to default.

[Garry Yao]

It's a regression, caused by our immediate selection change event in v4, but the culprit is instead inside of list block impl.

[Frederico Caldeira Knabben]

The list block implementation is not wrong. It is just considering a feature which we're not using on any of our plugins, where non-multiselect lists don't have the toggle effect (like select boxes).

But considering that we're not using that feature, we can accept this change, because all our combos act like selection boxes with toggle behavior. If we'll have troubles with this, we'll be able to revert this and try another approach.

[Garry Yao]

Fixed on master with

​https://github.com/ckeditor/ckeditor-dev/commit/6ebe811e092101a1488cc88a2241e54b7a570741