add convexity logic and tests for scalar max, Inf, and NaN

add convexity logic and tests for scalar max, Inf, and NaN

PathOps relies on isConvex() only returning true for trivially
convex paths. The old logic also returns true if the paths that
contain NaNs and Infinities. Return kUnknown_Convexity instead
in those cases and in cases where the convexity logic computes
intermediaries that overflow.

Committed: https://skia.googlesource.com/skia/+/d3d1a988b1ed144b0123dbe594c3a47a63d6451d

[caryclark, 2014-12-05 20:07:23]

caryclark@google.com changed reviewers:
+ bsalomon@google.com, robertphillips@google.com

[bsalomon, 2014-12-05 20:23:46]

https://codereview.chromium.org/784593002/diff/1/src/core/SkPath.cpp
File src/core/SkPath.cpp (right):

https://codereview.chromium.org/784593002/diff/1/src/core/SkPath.cpp#newcode2248
src/core/SkPath.cpp:2248: fIsFinite = false;
Do we need to track fIsFinite or can this just be

fConvexity = kConcave_Convexity;
return;

?

[bsalomon, 2014-12-05 20:40:26]

lgtm

[caryclark, 2014-12-08 12:48:25]

The CQ bit was checked by caryclark@google.com

[commit-bot: I haz the power, 2014-12-08 12:48:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/784593002/1

[commit-bot: I haz the power, 2014-12-08 12:57:47]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/d3d1a988b1ed144b0123dbe594c3a47a63d6451d