fix non-square stroke rects (non-aa)

fiddle showing bug: https://fiddle.skia.org/c/a21ecf5e33da84f52eba26e8c2f3d280

BUG=skia:5408
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2060543002

Review-Url: https://codereview.chromium.org/2060543002
2 files changed