Fix: Fixed View#render collision when moving focus from a one editable to the other in multi-root editor

[oskarwrobel]

Suggested merge commit message (convention)

Fix: Fixed View#render collision when moving focus from a one editable to the other in multi-root editor. Closes ckeditor/ckeditor5#1676.

---

Additional information

For example – encountered issues, assumptions you had to make, other affected tickets, etc.

[Reinmar]

Pity that you modified an existing test case. Unless it was bad, it'd make sense to have two here.

[oskarwrobel]

I created two tests first. But the second one included the first one so there was no point to keep it separately.

[Reinmar]

I don't buy it 😜 There could be two tests as long as they do something a bit different, and focus on bit different scenarios, even if today they boil down to the same thing, in the future they may bo covering different things.

[oskarwrobel]

It's not a different scenario. It's the same scenario (toggling class on editable) but the test was not good enough to find a bug. Now it is.