This is for the case where we have a zero-length range in between two
siblings, and we need to know what index that corresponds to in order to
be able to insert nodes there (rebuildNodes() will use it for this
purpose)
Change-Id: I357d1cd665667a76f955a10b8d9d2810976cdbd7
Selecting a zero-length range at the start or end of a text node
(e.g. (1,1)) would return the text node's parent instead of the text
node
Change-Id: I7fe089bf66b93185dd3415eff53aa7e04e3ffdb2