[chrome/browser/local_discovery] Replace MessageLoopProxy usage with ThreadTaskRunnerHandle

Replace MessageLoopProxy usage with ThreadTaskRunnerHandle in chrome/browser/local_discovery module.

MessageLoopProxy is deprecated.
This basically does a search and replace:

MessageLoopProxy::current() -> ThreadTaskRunnerHandle::Get().

BUG=391045
Committed: https://crrev.com/1a20d357839cd60272648164ed9f2167505b5b54
Cr-Commit-Position: refs/heads/master@{#328275}

[Pranay, 2015-05-04 09:17:26]

pranay.kumar@samsung.com changed reviewers:
+ vitalybuka@chromium.org

[Pranay, 2015-05-04 09:17:26]

PTAL,

Thanks

[Vitaly Buka (NO REVIEWS), 2015-05-04 15:40:52]

lgtm

[Pranay, 2015-05-04 17:26:35]

The CQ bit was checked by pranay.kumar@samsung.com

[commit-bot: I haz the power, 2015-05-04 17:27:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1127553002/1

[commit-bot: I haz the power, 2015-05-04 17:47:33]

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

[commit-bot: I haz the power, 2015-05-04 17:47:34]

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

[Pranay, 2015-05-05 03:33:36]

The CQ bit was checked by pranay.kumar@samsung.com

[Pranay, 2015-05-05 03:33:37]

The patchset sent to the CQ was uploaded after l-g-t-m from
vitalybuka@chromium.org
Link to the patchset: https://codereview.chromium.org/1127553002/#ps20001
(title: "Fixed Build break : Dependency in components/wifi classes")

[commit-bot: I haz the power, 2015-05-05 03:33:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1127553002/20001

[commit-bot: I haz the power, 2015-05-05 04:39:58]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-05 04:40:48]

Patchset 2 (id:??) landed as
https://crrev.com/1a20d357839cd60272648164ed9f2167505b5b54
Cr-Commit-Position: refs/heads/master@{#328275}