vp9_subtract_test,cosmetics: fix class order, casts
vp9_subtract_test,cosmetics: fix class order, casts

+ remove obsolete FIXME

Change-Id: I97ceb94b0e7860167e9c8cc6900bec8d155f0e8f

webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx