Fix build failure on linux_arm_cross_compile.

Fix build failure on linux_arm_cross_compile.

I recently added a test that uses pthread_t without including the pthread.h
header. This appears to be causing failures on the linux_arm_cross_compile bot.

BUG=394130
Committed: https://crrev.com/41fb6e1fed25724195f67fb6046b3f7d13085d43
Cr-Commit-Position: refs/heads/master@{#293561}

[teravest, 2014-09-05 13:06:30]

teravest@chromium.org changed reviewers:
+ mseaborn@chromium.org

[Mark Seaborn, 2014-09-05 14:20:32]

LGTM, thanks.  How about setting BUG=394130?

[teravest, 2014-09-05 14:22:35]

On 2014/09/05 14:20:32, Mark Seaborn wrote:
> LGTM, thanks.  How about setting BUG=394130?

Done.

[teravest, 2014-09-05 14:22:37]

The CQ bit was checked by teravest@chromium.org

[commit-bot: I haz the power, 2014-09-05 14:29:29]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/teravest@chromium.org/535643005/1

[commit-bot: I haz the power, 2014-09-05 16:24:46]

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

[commit-bot: I haz the power, 2014-09-05 16:24:46]

Try jobs failed on following builders:
  android_dbg_tests_recipe on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_dbg_tes...)

[teravest, 2014-09-05 16:31:33]

The CQ bit was checked by teravest@chromium.org

[commit-bot: I haz the power, 2014-09-05 16:32:32]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/teravest@chromium.org/535643005/1

[commit-bot: I haz the power, 2014-09-05 18:43:23]

Committed patchset #1 (id:1) as 8a1cf0ff697270f39c43ad664097b05eb32ad96a

[commit-bot: I haz the power, 2014-09-10 03:40:56]

Patchset 1 (id:??) landed as
https://crrev.com/41fb6e1fed25724195f67fb6046b3f7d13085d43
Cr-Commit-Position: refs/heads/master@{#293561}