break ambiguous angle sorting loop

A pair of cubics may be difficult to sort if the tangents suggest
one sort but the midpoints suggest a different one. When in this
gray area, and when the cumulative sort of all the angles fails to
resolve, reverse the sort to break the tie.

Before, when tiger8 was run through the signed distance field
generated directly from the path data, the simplify call might
hang since the angle could not be resolved. If the endless loop
is detected, and if there is no tie to break, just fail instead.

TBR=reed@google.com
BUG=skia:5131
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2426753002

Review-Url: https://codereview.chromium.org/2426753002
11 files changed