move mutex construction out of the benchmarks.

move mutex construction out of the benchmarks.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/a16e8bcef165aabb2463339e80fdd6f1fa19b8b9

[mtklein_C, 2015-09-22 16:02:16]

mtklein@chromium.org changed reviewers:
+ herb@google.com

[mtklein_C, 2015-09-22 16:05:58]

The CQ bit was checked by mtklein@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-09-22 16:06:09]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1345853004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1345853004/20001

[commit-bot: I haz the power, 2015-09-22 16:11:02]

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

[commit-bot: I haz the power, 2015-09-22 16:11:03]

Dry run: This issue passed the CQ dry run.

[herb_g, 2015-09-22 17:37:42]

lgtm

[mtklein, 2015-09-22 17:37:56]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-09-22 17:38:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1345853004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1345853004/20001

[commit-bot: I haz the power, 2015-09-22 17:38:51]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/a16e8bcef165aabb2463339e80fdd6f1fa19b8b9