Downgrade EV if the cert has gone missing
Downgrade EV if the cert has gone missing

This prevents a crash when reading the EV cert name for a cert that is
no longer in the cert store. In other words, we ensure that we never
return a security level of EV_SECURE unless the cert exists.

BUG=529664

Review URL: https://codereview.chromium.org/1413883004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#355707}

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