[whatwg] Control over selection direction

[Marijn Haverbeke]

> This sounds good to me.  I used the term "forwards" and "backwards"
> for the DOM Range spec, which I think make more sense.  I also think
> selectionDirection is a better property name, as Ojan suggests.

Coincidentally, that was exactly what I was going to propose at first,
but then I found the "top"/"bottom" thing made the concepts slightly
easier to explain ("where is the anchor" vs "if it goes in this
direction, that means the anchor is ..."). Anyway, I'm fine with your
proposed terminology too.