Add Valgrind suppression for an uninit.

BUG=330846
TBR=komatsu@chromium.org

Review URL: https://codereview.chromium.org/121693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242614 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242614