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

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

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

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

MessageLoopProxy -> SingleThreadTaskRunner

BUG=391045
Committed: https://crrev.com/68aa5e70ff9d3f49745cb4e83af1f4ce99928a56
Cr-Commit-Position: refs/heads/master@{#327654}

[Pranay, 2015-04-29 06:13:36]

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

[Pranay, 2015-04-29 06:13:37]

PTAL

Thanks

[xiyuan, 2015-04-29 15:57:28]

lgtm

[Pranay, 2015-04-29 16:27:13]

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

[Pranay, 2015-04-29 16:27:26]

Thanks :)

[commit-bot: I haz the power, 2015-04-29 16:27:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1117543003/1

[commit-bot: I haz the power, 2015-04-29 17:01:43]

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

[commit-bot: I haz the power, 2015-04-29 17:01:44]

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

[Pranay, 2015-04-30 04:39:11]

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

[Pranay, 2015-04-30 04:39:11]

The patchset sent to the CQ was uploaded after l-g-t-m from xiyuan@chromium.org
Link to the patchset: https://codereview.chromium.org/1117543003/#ps20001
(title: "Fixed build break")

[commit-bot: I haz the power, 2015-04-30 04:39:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1117543003/20001

[commit-bot: I haz the power, 2015-04-30 05:57:32]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-30 05:58:41]

Patchset 2 (id:??) landed as
https://crrev.com/68aa5e70ff9d3f49745cb4e83af1f4ce99928a56
Cr-Commit-Position: refs/heads/master@{#327654}