Make ONCCertificateImporter async.

Make ONCCertificateImporter async.

2nd Reland of https://codereview.chromium.org/547553005/
after fixing memory issues.

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
TBR=eroman@chromium.org

Committed: https://crrev.com/197fa5f4d6499ab91ae2435d82dda19fd60d9271
Cr-Commit-Position: refs/heads/master@{#296405}

[pneubeck (no reviews), 2014-09-24 12:50:58]

pneubeck@chromium.org changed reviewers:
+ joaodasilva@chromium.org

[pneubeck (no reviews), 2014-09-24 12:50:59]

this time verified with a local valgrind run.

[Joao da Silva, 2014-09-24 13:20:17]

lgtm

[pneubeck (no reviews), 2014-09-24 13:22:29]

pneubeck@chromium.org changed reviewers:
+ eroman@chromium.org

[pneubeck (no reviews), 2014-09-24 13:22:30]

TBR'ing eroman@, because other files than the unit test didn't change.

[pneubeck (no reviews), 2014-09-24 13:22:35]

The CQ bit was checked by pneubeck@chromium.org

[commit-bot: I haz the power, 2014-09-24 13:23:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/600803002/20001

[commit-bot: I haz the power, 2014-09-24 13:51:17]

Committed patchset #2 (id:20001) as 8ce00528fdaa8cf57cacf756dac14ea89f735974

[commit-bot: I haz the power, 2014-09-24 13:51:48]

Patchset 2 (id:??) landed as
https://crrev.com/197fa5f4d6499ab91ae2435d82dda19fd60d9271
Cr-Commit-Position: refs/heads/master@{#296405}