Adding DCHECK for CurrentlyOn(BrowserThread::IO)

Adding DCHECK for CurrentlyOn(BrowserThread::IO)

Fixing the below TODO:
TODO(rlp): Add DCHECK for CurrentlyOn(BrowserThread::IO) when the
ProfileManagerTest has been updated with a mock profile.

BUG=None

Committed: https://crrev.com/b611ff37a166f2479a3ff7686de09baf92ec893a
Cr-Commit-Position: refs/heads/master@{#327894}

[anujsharma, 2015-04-30 09:41:38]

anujk.sharma@samsung.com changed reviewers:
+ rsleevi@chromium.org

[anujsharma, 2015-04-30 09:41:38]

PTAL

[Ryan Sleevi, 2015-04-30 16:32:01]

lgtm

[anujsharma, 2015-05-01 06:48:46]

The CQ bit was unchecked by anujk.sharma@samsung.com

[anujsharma, 2015-05-01 06:48:47]

The CQ bit was checked by anujk.sharma@samsung.com

[anujsharma, 2015-05-01 06:48:50]

The CQ bit was checked by anujk.sharma@samsung.com

[anujsharma, 2015-05-01 06:49:04]

The CQ bit was unchecked by anujk.sharma@samsung.com

[anujsharma, 2015-05-01 06:49:06]

The CQ bit was checked by anujk.sharma@samsung.com

[commit-bot: I haz the power, 2015-05-01 06:49:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1115113002/20001

[commit-bot: I haz the power, 2015-05-01 08:33:39]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-01 08:34:33]

Patchset 2 (id:??) landed as
https://crrev.com/b611ff37a166f2479a3ff7686de09baf92ec893a
Cr-Commit-Position: refs/heads/master@{#327894}