improve sanity checks on gradient constructor parameters

improve sanity checks on gradient constructor parameters

BUG=445807
Committed: https://skia.googlesource.com/skia/+/1b74730c6bc1de0b638c4c6e18e71f520bb18249

[reed1, 2015-01-06 14:46:36]

reed@google.com changed reviewers:
+ senorblanco@chromium.org

[reed1, 2015-01-06 14:46:52]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2015-01-06 14:47:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/837013002/1

[commit-bot: I haz the power, 2015-01-06 14:47:26]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-01-06 20:47 UTC

[Stephen White, 2015-01-06 14:53:30]

https://codereview.chromium.org/837013002/diff/1/src/effects/gradients/SkGrad...
File src/effects/gradients/SkGradientShader.cpp (right):

https://codereview.chromium.org/837013002/diff/1/src/effects/gradients/SkGrad...
src/effects/gradients/SkGradientShader.cpp:740: static bool valid_grad(const
SkColor colors[], const SkScalar pos[], int count, unsigned tileMode) {
Nit: pos is unused here (presumably because NULL is always valid).

[Stephen White, 2015-01-06 15:01:27]

LGTM

[commit-bot: I haz the power, 2015-01-06 15:13:22]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/1b74730c6bc1de0b638c4c6e18e71f520bb18249