Ckeditor5: No selectionchange on Firefox

[pjasiun]

As a result of a research (https://github.com/ckeditor/ckeditor5-engine/issues/315) we found out there is no selectionchange on Firefox by default (https://bugzilla.mozilla.org/show_bug.cgi?id=571294#c57), user need to change dom.select_events.enabled setting in the browser to enable it.

Therefore, selection observer (https://github.com/ckeditor/ckeditor5-engine/issues/310) will not properly without a polyfill (https://github.com/ckeditor/ckeditor5-engine/issues/315#issuecomment-212465509).

If Firefox will not support selectionchange soon we will need to introduce such polyfill in our code.

[Reinmar]

This makes for an iteration 3 ticket, because iteration 3 will be about browser compatibility.

[Reinmar]

It seems that selectionchange may land in Firefox veeeeery soon (https://bugzilla.mozilla.org/show_bug.cgi?id=1242718) so:

1. Let's wait to have some confirmation when that may happen.
2. If that's too long from now, let's not spend too much time on this anyway, as it finally seems that we'll have 100% native support.

[Reinmar]

I gently asked FF team to release the feature https://bugzilla.mozilla.org/show_bug.cgi?id=1231923#c16 :D

[Reinmar]

The issue to track now is https://bugzilla.mozilla.org/show_bug.cgi?id=1309612. And the response is very promising https://bugzilla.mozilla.org/show_bug.cgi?id=1231923#c17 :)))

[Reinmar]

https://developer.mozilla.org/en-US/Firefox/Releases/52 – so the event will ship in March :)

[Reinmar]

FF 52 was released and everything is fine.