use pathops utils to improve precision of cubic chopping in scan converter

use pathops utils to improve precision of cubic chopping in scan converter

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/dc3088570f945ed0ede84f0af0016eedc267dda3

[reed1, 2015-04-29 21:32:45]

reed@google.com changed reviewers:
+ caryclark@google.com

[reed1, 2015-04-29 21:32:45]

wip .. more to come

[reed1, 2015-04-30 12:49:32]

The CQ bit was checked by reed@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-04-30 12:49:48]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1113963002/20001

[commit-bot: I haz the power, 2015-04-30 12:53:58]

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

[commit-bot: I haz the power, 2015-04-30 12:53:59]

Dry run: This issue passed the CQ dry run.

[reed1, 2015-04-30 12:56:47]

ptal

[caryclark, 2015-04-30 12:59:41]

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp
File src/core/SkGeometry.cpp (right):

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp#new...
src/core/SkGeometry.cpp:924: const Sk2s three(3);
unused variable?

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp#new...
src/core/SkGeometry.cpp:938: static SkPoint dpoint_to_point(const SkDPoint& src)
{
this is the same as

src.asSkPoint()

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp#new...
src/core/SkGeometry.cpp:944: int roots = SkDCubic::RootsValidT(coeff[0],
coeff[1], coeff[2], coeff[3], t);
This doesn't take into account the case where the roots miss the end because of
numerical imprecision. Consider instead:

SkDCubic cubic;
cubic.set(src);
int roots = LineCubicIntersections::HorizontalIntersect(src, y, t)

and 

int roots = LineCubicIntersections::VerticalIntersect(src, y, t)

[caryclark, 2015-04-30 13:03:00]

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp
File src/core/SkGeometry.cpp (right):

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp#new...
src/core/SkGeometry.cpp:944: int roots = SkDCubic::RootsValidT(coeff[0],
coeff[1], coeff[2], coeff[3], t);
On 2015/04/30 12:59:41, caryclark wrote:
 int roots = LineCubicIntersections::HorizontalIntersect(cubic, y, t)
 int roots = LineCubicIntersections::VerticalIntersect(cubic, y, t)

(fixed typos)

[reed1, 2015-04-30 13:34:22]

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp
File src/core/SkGeometry.cpp (right):

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp#new...
src/core/SkGeometry.cpp:924: const Sk2s three(3);
On 2015/04/30 12:59:41, caryclark wrote:
> unused variable?

Done.

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp#new...
src/core/SkGeometry.cpp:938: static SkPoint dpoint_to_point(const SkDPoint& src)
{
On 2015/04/30 12:59:40, caryclark wrote:
> this is the same as
> 
> src.asSkPoint()

Done.

https://codereview.chromium.org/1113963002/diff/1/src/core/SkGeometry.cpp#new...
src/core/SkGeometry.cpp:944: int roots = SkDCubic::RootsValidT(coeff[0],
coeff[1], coeff[2], coeff[3], t);
On 2015/04/30 13:03:00, caryclark wrote:
> On 2015/04/30 12:59:41, caryclark wrote:
>  int roots = LineCubicIntersections::HorizontalIntersect(cubic, y, t)
>  int roots = LineCubicIntersections::VerticalIntersect(cubic, y, t)
> 
> (fixed typos)

Done.

[reed1, 2015-04-30 13:35:34]

The CQ bit was checked by reed@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-04-30 13:35:49]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1113963002/40001

[caryclark, 2015-04-30 13:37:58]

lgtm

[reed1, 2015-04-30 14:13:55]

The CQ bit was unchecked by reed@google.com

[reed1, 2015-04-30 14:14:00]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2015-04-30 14:14:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1113963002/40001

[commit-bot: I haz the power, 2015-04-30 14:47:17]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/dc3088570f945ed0ede84f0af0016eedc267dda3