Change the operations touching counts_[] and redundant_count_ to be atomic.
This will make it explicit that the counters are accessed without synchronization and will also suppress TSan v2 warnings.

BUG=46840
R=jar@chromium.org,kaiwang@chromium.org

Review URL: https://codereview.chromium.org/116983004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245997 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245997
Automated Commit: Committing new LKGM version 5268.0.0 for chromeos.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245998 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245998