Get rid of unnecessary explicit TearDown in OffDomainInclusionDetectorTest.

Get rid of unnecessary explicit TearDown in OffDomainInclusionDetectorTest.

Somehow the exact diff in this CL is what made patch set 4 land while patch
set 3 was failing ASAN @ https://codereview.chromium.org/836963003... but
re-investigated on Matt's request and now all bots are green without it...

TBR=mattm
BUG=412468
Committed: https://crrev.com/030eed4d29c60b337e1effeb49cff806a412f3c3
Cr-Commit-Position: refs/heads/master@{#312228}

[gab, 2015-01-20 18:33:52]

gab@chromium.org changed reviewers:
+ mattm@chromium.org

[gab, 2015-01-20 18:34:26]

TBR mattm: going to try to land this, we'll see... very weird that it passes now
and failed before...

Cheers,
Gab

[gab, 2015-01-20 18:34:30]

The CQ bit was checked by gab@chromium.org

[commit-bot: I haz the power, 2015-01-20 18:34:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/848063002/40001

[commit-bot: I haz the power, 2015-01-20 18:50:57]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-01-20 18:52:10]

Patchset 3 (id:??) landed as
https://crrev.com/030eed4d29c60b337e1effeb49cff806a412f3c3
Cr-Commit-Position: refs/heads/master@{#312228}