make SkColorShader private, use public factory

make SkColorShader private, use public factory

BUG=skia:

Need https://codereview.chromium.org/785823002/ to land first

Committed: https://skia.googlesource.com/skia/+/b9bb38cd187bfd43abfa8577da0ab4e34d181073

[reed2, 2014-12-07 20:54:08]

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

[reed2, 2014-12-07 20:54:27]

The CQ bit was checked by reed@chromium.org

[commit-bot: I haz the power, 2014-12-07 20:54:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/788533002/1

[commit-bot: I haz the power, 2014-12-07 20:54:55]

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 2014-12-08 02:54 UTC

[reed2, 2014-12-07 20:55:30]

The CQ bit was unchecked by reed@chromium.org

[f(malita), 2014-12-08 00:51:24]

fmalita@chromium.org changed reviewers:
+ fmalita@chromium.org

[f(malita), 2014-12-08 00:51:25]

lgtm

[reed1, 2014-12-08 14:05:36]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2014-12-08 14:06:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/788533002/1

[commit-bot: I haz the power, 2014-12-08 14:06:42]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/b9bb38cd187bfd43abfa8577da0ab4e34d181073