Add Early DNS prefetching to ChromeShell.

Add Early DNS prefetching to ChromeShell.

The actual code was added in https://codereview.chromium.org/909893003
and enabled downstream, but not in ChromeShell.

BUG=458216
Committed: https://crrev.com/151fdce9acc177ad20f223f13b74dbcfde50a76e
Cr-Commit-Position: refs/heads/master@{#327251}

[Benoit L, 2015-03-24 13:32:33]

Hello nyquist,

Just a small CL enabling Early DNS in ChromeShell. This was left out in the
original CL for no good reason.

Thanks!

[Benoit L, 2015-04-21 13:48:25]

Hello nyquist,

Just a small CL enabling Early DNS in ChromeShell. This was left out from the
original CL for no good reason.

Thanks!

[Benoit L, 2015-04-21 13:48:43]

lizeb@chromium.org changed reviewers:
+ nyquist@chromium.org

[Benoit L, 2015-04-21 13:48:43]

Hello nyquist,

Just a small CL enabling Early DNS in ChromeShell. This was left out from the
original CL for no good reason.

Thanks!

[nyquist, 2015-04-23 00:28:18]

lgtm

[Benoit L, 2015-04-28 08:40:17]

The CQ bit was checked by lizeb@chromium.org

[commit-bot: I haz the power, 2015-04-28 08:40:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1029583006/1

[commit-bot: I haz the power, 2015-04-28 08:43:03]

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

[commit-bot: I haz the power, 2015-04-28 08:43:03]

Try jobs failed on following builders:
  ios_dbg_simulator_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_dbg_simulator...)

[Benoit L, 2015-04-28 09:00:00]

The CQ bit was checked by lizeb@chromium.org

[Benoit L, 2015-04-28 09:00:00]

The patchset sent to the CQ was uploaded after l-g-t-m from nyquist@chromium.org
Link to the patchset: https://codereview.chromium.org/1029583006/#ps20001
(title: "Rebase")

[commit-bot: I haz the power, 2015-04-28 09:00:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1029583006/20001

[commit-bot: I haz the power, 2015-04-28 09:27:15]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-28 09:28:06]

Patchset 2 (id:??) landed as
https://crrev.com/151fdce9acc177ad20f223f13b74dbcfde50a76e
Cr-Commit-Position: refs/heads/master@{#327251}