fix last skp bug

Fix last pathops skp bug

This fixes the last bug discovered by iterating through the 800K
skp corpus representing the top 1M websites. For every clip on the
stack, the paths are replaced with the pathop intersection. The
resulting draw is compared with the original draw for pixel errors.

At least two prominent bugs remain. In one, the winding value is
confused by a cubic with an inflection. In the other, a quad/cubic
pair, nearly coincident, fails to find an intersection.

These minor changes include ignoring very tiny self-intersections
of cubics, and processing degenerate edges that don't connect to
anything else.

TBR=reed

Committed: https://skia.googlesource.com/skia/+/e4097e3a0b10bb0047a45b6949ca01826f0807a7

[caryclark, 2014-06-18 14:13:51]

The CQ bit was checked by caryclark@google.com

[commit-bot: I haz the power, 2014-06-18 14:14:16]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/caryclark@google.com/340103002/1

[commit-bot: I haz the power, 2014-06-18 14:24:25]

Change committed as e4097e3a0b10bb0047a45b6949ca01826f0807a7