rAc: fix postal code validation.

R=estade@chromium.org
BUG=340425

Review URL: https://codereview.chromium.org/136113012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249147 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249147