Fix DCHECK(!config_watcher_) in HostProcess::~HostProcess().

Fix DCHECK(!config_watcher_) in HostProcess::~HostProcess().

When shutting down HostProcess config_watcher_ is supposed to be deleted
on the nework thread. Previously ShutdownOnNetworkThread() was deleting
it, but that line was mistakenly removed in crrev.com/302162 . Adding
it back.

Committed: https://crrev.com/846e3642f9f54db916a5141f26a368f1c7aa0095
Cr-Commit-Position: refs/heads/master@{#313623}

[Sergey Ulanov, 2015-01-28 19:00:16]

sergeyu@chromium.org changed reviewers:
+ kelvinp@chromium.org

[kelvinp, 2015-01-28 20:43:04]

lgtm

[Sergey Ulanov, 2015-01-28 20:46:48]

The CQ bit was checked by sergeyu@chromium.org

[commit-bot: I haz the power, 2015-01-28 20:47:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/885693003/1

[commit-bot: I haz the power, 2015-01-28 22:26:33]

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

[commit-bot: I haz the power, 2015-01-28 22:26:34]

Try jobs failed on following builders:
  linux_chromium_asan_rel on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Sergey Ulanov, 2015-01-28 23:18:26]

The CQ bit was checked by sergeyu@chromium.org

[commit-bot: I haz the power, 2015-01-28 23:19:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/885693003/1

[commit-bot: I haz the power, 2015-01-28 23:54:40]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-28 23:56:00]

Patchset 1 (id:??) landed as
https://crrev.com/846e3642f9f54db916a5141f26a368f1c7aa0095
Cr-Commit-Position: refs/heads/master@{#313623}