[css3-writing-modes] column progression direction

Alex Mogilevsky raised an issue in a discussion awhile back: specifically,
what should the column progression direction be if the parent of the
multi-column element belongs to an orthogonal flow with a block flow
direction opposite to the multi-col element's inline direction?

E.g. suppose I have a vertical Japanese document:


  ¦ ¦ ¦ ¦ ¦ V
  ¦ ¦ ¦ ¦ ¦ V
  ¦ ¦ ¦ ¦ ¦ V
  ¦ ¦ ¦ ¦ ¦ ¦
  ¦ ¦ ¦ ¦ ¦ ¦
    <====

Then I insert a horizontal (LTR) multicol element

>>>-- >>>-- ¦ ¦ ¦ ¦ ¦ V
----- ----- ¦ ¦ ¦ ¦ ¦ V
--A-- --B-- ¦ ¦ ¦ ¦ ¦ V
----- ----- ¦ ¦ ¦ ¦ ¦ ¦
----- ----- ¦ ¦ ¦ ¦ ¦ ¦
                <====

Is column A or B first in the logical order?

~fantasai