locateFragment

Where the element that href names is on screen: the page that shows its first line, and one rectangle per line of it on that page (#36). href is a zip path with a fragment, as EpubOverlayClip.textHref and EpubPage.links give it. An element without text of its own gives its page from the anchor map, with no rectangle. Null when the book has no such chapter or element. Lays out the chapter.