fix pathops fuzz failures

fix pathops fuzz failures

If a curve has the identical start and control points, the
initial or final tangent can't be trivally determined. The
perpendicular to the tangent is used to measure coincidence.

Add logic for cubics, quadratics, and conics, to use the
secondary control points or the end points if the initial
control point alone can't determine the tangent.

Add debugging (currently untriggered by exhaustive testing)
to detect zero-length tangents which are not at the curve
endpoints.

Increase the number of temporary intersecions gathered from
10 to 12 but reduce the max passed in by cubic intersection from
27 to 12. Also, add checks if the max passed exceeds the
storage allocated.

When cleaning up parallel lines, choose the intersection which
is on the end of both segments over the intersection which
is on the end of a single segment.

TBR=reed@google.com
BUG=425140, 516266
Committed: https://skia.googlesource.com/skia/+/94c902e63d77641cadd76155c2b248d04f63b560

[caryclark, 2015-08-18 13:46:36]

The CQ bit was checked by caryclark@google.com

[commit-bot: I haz the power, 2015-08-18 13:46:43]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1288863004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1288863004/1

[commit-bot: I haz the power, 2015-08-18 13:47:42]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-18 13:47:43]

Try jobs failed on following builders:
  Build-Ubuntu-GCC-Arm64-Debug-Android-Trybot on client.skia.compile
(JOB_FAILED,
http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-GCC-Arm...)
  Build-Ubuntu-GCC-Arm7-Debug-Android-Trybot on client.skia.compile (JOB_FAILED,
http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-GCC-Arm...)

[caryclark, 2015-08-18 14:06:18]

The CQ bit was checked by caryclark@google.com

[commit-bot: I haz the power, 2015-08-18 14:06:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1288863004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1288863004/20001

[commit-bot: I haz the power, 2015-08-18 14:12:46]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/94c902e63d77641cadd76155c2b248d04f63b560

[Will Harris, 2016-06-08 21:17:45]

On 2015/08/18 14:12:46, commit-bot: I haz the power wrote:
> Committed patchset #2 (id:20001) as
> https://skia.googlesource.com/skia/+/94c902e63d77641cadd76155c2b248d04f63b560

Why was this CL committed direct without review?