Fixed an assertion error in GrAAConvexTessellator. While adding a new point, it would check that the new point was not a duplicate of the previous point. It would then drop the previous point if it was in the middle of a straight line, and proceed to add the new point.

Unfortunately, floating point precision issues mean that sometimes, after dropping the previous point, we'd end up with the newly-added point as a duplicate of the new previous point, tripping an assertion failure.

BUG=skia:4732
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1557903002

Review URL: https://codereview.chromium.org/1557903002
1 file changed