Revert of Make ONCCertificateImporter async.

Revert of Make ONCCertificateImporter async. (patchset #5 id:190001 of https://codereview.chromium.org/547553005/)

Reason for revert:
Use-after-free.
https://code.google.com/p/chromium/issues/detail?id=415916

Original issue's description:
> Make ONCCertificateImporter async.
>
> This prepares for the new CertDatabase keyed service, which will have stricter threading restrictions. https://codereview.chromium.org/419013003/
>
> Before, ONCCertificateImporter accessed the NSSCertDatabase from the UI thread and blocked on certificate store operations.
>
> Now, the import itself is asychronous and calls back on completion.
>
> While there, this also removes the GMock of the importer.
>
> BUG=413219
>
> Committed: https://crrev.com/bc656c0e7b7bd67fb28e5a880d21b9510ebd3e3a
> Cr-Commit-Position: refs/heads/master@{#295534}

TBR=joaodasilva@chromium.org,eroman@chromium.org,pneubeck@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=413219
Committed: https://crrev.com/7075322754d57ae4dc55001d9ef5d596fd07f588
Cr-Commit-Position: refs/heads/master@{#295683}

[eugenis, 2014-09-19 09:14:48]

Created Revert of Make ONCCertificateImporter async.

[commit-bot: I haz the power, 2014-09-19 09:16:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/580283005/1

[commit-bot: I haz the power, 2014-09-19 09:16:49]

Committed patchset #1 (id:1) as d4f610934e323b8a53db9e839190316e52477293

[commit-bot: I haz the power, 2014-09-19 09:17:25]

Patchset 1 (id:??) landed as
https://crrev.com/7075322754d57ae4dc55001d9ef5d596fd07f588
Cr-Commit-Position: refs/heads/master@{#295683}