Fix race in supports_simd().

Fix race in supports_simd().

Local statics are not thread safe in Chrome.  Use an SkLazyPtr instead.

See https://code.google.com/p/chromium/issues/detail?id=418041

BUG=418041
Committed: https://skia.googlesource.com/skia/+/c09e2af17fab03d3d36c20e5201a560c3e4c233e

[mtklein, 2014-10-13 14:27:44]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-10-13 14:28:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/655573002/1

[commit-bot: I haz the power, 2014-10-13 14:28:49]

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 2014-10-13 20:28 UTC

[commit-bot: I haz the power, 2014-10-13 14:30:29]

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

[commit-bot: I haz the power, 2014-10-13 14:30:30]

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

[mtklein, 2014-10-13 14:34:03]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-10-13 14:34:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/655573002/130001

[commit-bot: I haz the power, 2014-10-13 14:34:50]

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 2014-10-13 20:34 UTC

[mtklein, 2014-10-13 14:38:09]

mtklein@google.com changed reviewers:
+ bungeman@google.com

[bungeman-skia, 2014-10-13 14:59:01]

lgtm

[commit-bot: I haz the power, 2014-10-13 19:48:26]

Committed patchset #2 (id:130001) as c09e2af17fab03d3d36c20e5201a560c3e4c233e