fix for conic fuzz

A fuzzer generates a conic that hangs when drawn.
The quads that approximate the conics move up and down
in y, confusing the renderer.

This fix ensures that the split conic maintains the
same y direction as the original conic.

R=reed@google.com
BUG=647922
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2350263003

Review-Url: https://codereview.chromium.org/2350263003
2 files changed