Suppress Mac valgrind leaks.

BUG=310761
NOTRY=true
TBR=tapted@chromium.org

Review URL: https://codereview.chromium.org/37633003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230487 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230487