Expose Thread::using_external_message_loop() to subclasses.

Expose Thread::using_external_message_loop() to subclasses.

Extracted from https://codereview.chromium.org/2464233002/#ps260001 as I
flip flop back and forth between it and precursor CLs and having a change
in thread.h forces painful rebuilds...

BUG=653916
Committed: https://crrev.com/f7f153ec850decdcc9bbd2f874c7b8e219bb321d
Cr-Commit-Position: refs/heads/master@{#430960}

[gab, 2016-11-09 16:16:45]

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

[commit-bot: I haz the power, 2016-11-09 16:17:02]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[gab, 2016-11-09 16:17:20]

gab@chromium.org changed reviewers:
+ mark@chromium.org

[gab, 2016-11-09 16:17:21]

Mark PTAL, thanks!

[Mark Mentovai, 2016-11-09 16:55:54]

LGTM

[gab, 2016-11-09 16:56:52]

The CQ bit was unchecked by gab@chromium.org

[gab, 2016-11-09 16:56:56]

The CQ bit was checked by gab@chromium.org

[commit-bot: I haz the power, 2016-11-09 16:57:25]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-09 17:30:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-11-09 17:32:36]

Description was changed from

==========
Expose Thread::using_external_message_loop() to subclasses.

Extracted from https://codereview.chromium.org/2464233002/#ps260001 as I
flip flop back and forth between it and precursor CLs and having a change
in thread.h forces painful rebuilds...

BUG=653916
==========

to

==========
Expose Thread::using_external_message_loop() to subclasses.

Extracted from https://codereview.chromium.org/2464233002/#ps260001 as I
flip flop back and forth between it and precursor CLs and having a change
in thread.h forces painful rebuilds...

BUG=653916

Committed: https://crrev.com/f7f153ec850decdcc9bbd2f874c7b8e219bb321d
Cr-Commit-Position: refs/heads/master@{#430960}
==========

[commit-bot: I haz the power, 2016-11-09 17:32:37]

Patchset 1 (id:??) landed as
https://crrev.com/f7f153ec850decdcc9bbd2f874c7b8e219bb321d
Cr-Commit-Position: refs/heads/master@{#430960}