Replace ASSERT()s with DCHECK*() in core/html/imports/.

Replace ASSERT()s with DCHECK*() in core/html/imports/.

This CL has no behavior changes.

BUG=596760
Committed: https://crrev.com/c8dd9554617bcac53dea5173d382d7e66b96109f
Cr-Commit-Position: refs/heads/master@{#413095}

[tkent, 2016-08-19 05:19:42]

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

[commit-bot: I haz the power, 2016-08-19 05:20:11]

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

[tkent, 2016-08-19 08:20:37]

tkent@chromium.org changed reviewers:
+ kochi@chromium.org

[tkent, 2016-08-19 08:20:38]

kochi@, would you review this please?

[commit-bot: I haz the power, 2016-08-19 08:59:51]

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

[commit-bot: I haz the power, 2016-08-19 08:59:52]

Dry run: This issue passed the CQ dry run.

[kochi, 2016-08-19 09:53:14]

The CQ bit was checked by kochi@chromium.org

[kochi, 2016-08-19 09:53:15]

lgtm

[commit-bot: I haz the power, 2016-08-19 09:53:37]

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, 2016-08-19 09:57:24]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-19 09:58:58]

Description was changed from

==========
Replace ASSERT()s with DCHECK*() in core/html/imports/.

This CL has no behavior changes.

BUG=596760
==========

to

==========
Replace ASSERT()s with DCHECK*() in core/html/imports/.

This CL has no behavior changes.

BUG=596760

Committed: https://crrev.com/c8dd9554617bcac53dea5173d382d7e66b96109f
Cr-Commit-Position: refs/heads/master@{#413095}
==========

[commit-bot: I haz the power, 2016-08-19 09:58:59]

Patchset 1 (id:??) landed as
https://crrev.com/c8dd9554617bcac53dea5173d382d7e66b96109f
Cr-Commit-Position: refs/heads/master@{#413095}