compare degenerates with tolerance

Conics with very large w values can
be approximated with two straight lines.

This avoids iterating endlessly in an
attempt to create quadratics with unstable
numerics.

Check to see if the first chop generated
a pair of lines within the default
point comparison tolerance.

R=reed@google.com
BUG=643933, 643665
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2312923002

Review-Url: https://codereview.chromium.org/2312923002
2 files changed