Remove dom_utils.

Remove dom_utils.

1) These types of operations shouldn't be done in the content API.

2) The last call site no longer needs it in Blink after
https://codereview.chromium.org/1208423015 landed.

R=jochen,jam
BUG=508151
Committed: https://crrev.com/bdaac789c082c37217de4d1128c3230764c1697e
Cr-Commit-Position: refs/heads/master@{#337988}

[dglazkov, 2015-07-08 18:12:25]

Whoops, needs a rebase to remove the under-patch.

[dglazkov, 2015-07-08 21:05:19]

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

[commit-bot: I haz the power, 2015-07-08 21:06:43]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1223033002/20001

[commit-bot: I haz the power, 2015-07-08 22:43:30]

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

[commit-bot: I haz the power, 2015-07-08 22:43:30]

Dry run: This issue passed the CQ dry run.

[dglazkov, 2015-07-08 22:47:15]

On 2015/07/08 at 22:43:30, commit-bot wrote:
> Dry run: This issue passed the CQ dry run.

PTAL.

[jochen (gone - plz use gerrit), 2015-07-09 04:01:15]

lgtm

[dglazkov, 2015-07-09 05:08:48]

The CQ bit was checked by dglazkov@chromium.org

[commit-bot: I haz the power, 2015-07-09 05:09:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1223033002/20001

[commit-bot: I haz the power, 2015-07-09 05:13:19]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-07-09 05:14:16]

Patchset 2 (id:??) landed as
https://crrev.com/bdaac789c082c37217de4d1128c3230764c1697e
Cr-Commit-Position: refs/heads/master@{#337988}