Add test for QuickFDot6Div

This test will catch our (1 << 10) bug (which should be 1 << 9)

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4986

Change-Id: I25b607d1535a647284cee3b304a6f567f389e7f6
Reviewed-on: https://skia-review.googlesource.com/4986
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
5 files changed