zygote: use pthread_once to init localtime(_r) functions.
zygote: use pthread_once to init localtime(_r) functions.

The previous trick (thread safe statics) is disabled via
compiler flags in our build.

BUG=54264
TEST=none

http://codereview.chromium.org/3412017

git-svn-id: http://src.chromium.org/svn/trunk/src@60076 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: f5593d3d14b5945d4180b5134604b23a1cfdcf9e
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser