[FF] NS_ERROR_FAILURE thrown randomly when setting DOM selection

[scofalik]

📝 Provide detailed reproduction steps (if any)

We had problems with NS_ERROR_FAILURE thrown on random occasions, some of them seems fixed (closed issues in this repository), and at least one error is not closed (https://github.com/cksource/collaboration-features/issues/4183).

When testing multi-root editor in RTC environment, this happened again, this time, when removing the last root and performing undo. It seems to not be 100%, but it mostly throws when you do it right. It is an edge case but that's not entirely the point.

The point is that the error is not described and it is hard to find any information about when it would be thrown.

The error is thrown in renderer.ts in _updateDomSelection:

domSelection.collapse( anchor.parent, anchor.offset );
domSelection.extend( focus.parent, focus.offset );

I checked and anchor and focus are set correctly. The DOM elements have same owner document and it is the same as the selection. Everything seems right.

One suggestion I did find when looking for the solution is to use setBaseAndExtent instead. After using it, I wasn't able to reproduce this problem anymore.

Maybe we will be able to fix random FF bugs this way?

[Witoso]

@scofalik could it help solve #9635 in your opinion?

[scofalik]

I thought so initially, but I confused two different things, both being Firefox errors. This one is when we try to set DOM selection, the one you linked is when we want to read the DOM selection.