remove unused SkCullPoints

need to remove file references from chrome before landing this
https://codereview.chromium.org/1547603002#

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1541933004

TBR=scroggo

Review URL: https://codereview.chromium.org/1541933004
8 files changed