Add comments to explain the current handling of CERT_STATUS_NON_UNIQUE_NAME.

R=rsleevi@chromium.org
BUG=none
TEST=none

Review URL: https://codereview.chromium.org/98333009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241509 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241509