readingOrderOf

What a speech engine says for the element that href names: the text of that element in reading order, as EpubPage.readingOrder gives it, with the pronunciation hints of its spans (#525). A reading aloud speaks it for a media overlay clip without audio. An element over several pages gives the items of each page in turn. Images are left out. Empty when the book has no such chapter or element, or the element has no text. Lays out the chapter.