GitLab

Add acquire/release calls in one-time init for histograms

Clean up macros which do one-time initialization of
static pointer to histograms to use subtle atomic
operators.

r=willchan, dvyukov
BUG=7535006
Review URL: http://codereview.chromium.org/7535006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@95762 0039d316-1c4b-4281-b951-d872f2087c98