So far this looks to be the right solution.

1. Take the old CancelClose method and assign it to ConfirmClose.
2. Rewrite the logic in the new ConfirmClose so that the return value bool is reversed.
3. Write a new CancelClose, this for one reason only: if you want to perpetuate the behavior of TabBar of not allowing you to close the last tab. This needs a bit further investigation. The new CancelClose is something very simple, like testing how many tabs you have open:

bool EditorManager::OnCancelClose(Value val) {
	int count = tabFiles.GetCount();
	return count <= 1;
}

I also removed the *Some variant of these callbacks, these needs further investigation if they are of use to me.