cubic stroke fix

Normally parallel tangents means that the stroke can
be represented with a line. But looping cubics can
have parallel tangents if the loop is 180 degrees.

Check to see if the tangents direction is opposite
to subdivide further.

R=reed@google.com
BUG=skia:5099
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1862753002

Review URL: https://codereview.chromium.org/1862753002
2 files changed