Remove redundant and erroneous DCHECK

Remove redundant and erroneous DCHECK

reader_ can be null, and that's fine.

BUG=633142
Committed: https://crrev.com/9d7fd58d9bd9540890aa53a243e1a07408fba7eb
Cr-Commit-Position: refs/heads/master@{#428252}

[hubbe, 2016-10-27 23:46:12]

The CQ bit was checked by hubbe@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-10-27 23:46:42]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[hubbe, 2016-10-27 23:46:49]

hubbe@chromium.org changed reviewers:
+ dalecurtis@chromium.org

[DaleCurtis, 2016-10-27 23:50:13]

lgtm

[commit-bot: I haz the power, 2016-10-28 01:17:40]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-10-28 01:17:41]

Dry run: This issue passed the CQ dry run.

[hubbe, 2016-10-28 02:06:34]

The CQ bit was checked by hubbe@chromium.org

[commit-bot: I haz the power, 2016-10-28 02:06:56]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-28 02:22:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-10-28 02:24:32]

Description was changed from

==========
Remove redundant and erroneous DCHECK

reader_ can be null, and that's fine.

BUG=633142
==========

to

==========
Remove redundant and erroneous DCHECK

reader_ can be null, and that's fine.

BUG=633142

Committed: https://crrev.com/9d7fd58d9bd9540890aa53a243e1a07408fba7eb
Cr-Commit-Position: refs/heads/master@{#428252}
==========

[commit-bot: I haz the power, 2016-10-28 02:24:33]

Patchset 1 (id:??) landed as
https://crrev.com/9d7fd58d9bd9540890aa53a243e1a07408fba7eb
Cr-Commit-Position: refs/heads/master@{#428252}