Revive quad approximation stroker

This uses quad approximations of the outer and inner paths describing a stroke. Cubics and conics' thick strokes are approximated with quads as well.

The approximation uses a similar error term as the fill scan converter to determine the number of quads to use.

This also updates SampleApp QuadStroker test with conics, ovals, and stroked text.

Committed: https://skia.googlesource.com/skia/+/04e4d08556750ff6be4576a4cd4925964c63376f

[caryclark, 2015-02-18 21:15:51]

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

[reed1, 2015-02-19 22:25:19]

lgtm

[caryclark, 2015-02-20 13:48:24]

The CQ bit was checked by caryclark@google.com

[commit-bot: I haz the power, 2015-02-20 13:49:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/932113002/100001

[commit-bot: I haz the power, 2015-02-20 13:50:33]

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

[commit-bot: I haz the power, 2015-02-20 13:50:33]

Try jobs failed on following builders:
  Build-Ubuntu13.10-GCC4.8-x86_64-Release-Trybot on client.skia.compile
(JOB_FAILED,
http://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu13.10-GC...)

[caryclark, 2015-02-20 14:18:06]

New patchsets have been uploaded after l-g-t-m from reed@google.com

[caryclark, 2015-02-20 14:19:31]

The CQ bit was checked by caryclark@google.com

[commit-bot: I haz the power, 2015-02-20 14:20:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/932113002/120001

[commit-bot: I haz the power, 2015-02-20 14:34:01]

Committed patchset #7 (id:120001) as
https://skia.googlesource.com/skia/+/04e4d08556750ff6be4576a4cd4925964c63376f