[css3-background] box-decoration-break and bidi reordering

As I'm working through the css3-writing-modes spec, I noticed that we
don't address box-splitting due to bidi reordering in the definition
of 'box-decoration-break'.

Should we specify that 'box-decoration-break' applies also when bidi
reordering splits the inline box? Or specify that such splits are
always "sliced"?

~fantasai