[HarfBuzz] Mirroring brackets

[hasen j]

I ran into a problem where it seemed like HarfBuzz wasn't doing any
bracket mirroring for arabic runs/items, even though I set the
item.bidiLevel to 1.

When I looked at the code in harfbuzz-arabic.c, it seems to only do
mirroring in non-OT mode.


    #ifndef NO_OPENTYPE
        ....
        arabicSyrianOpenTypeShape(..) // doesn't do mirroring
        ....
        return
    #endif

        shapedString(..) // does mirroring

Is this a bug or the intended behavior? I noticed google chrome on
linux doesn't do bracket mirroring either.