[Merge to M53]arc: Add arc enable sync pref initial set up.

[Merge to M53]arc: Add arc enable sync pref initial set up.

Arc enable sync pref is false by default if user never modify sync settings. This
patch enables arc sync service to start when user never manually modify sync
settings.

BUG=642907
, http://b/31156650
TEST=Manual test on a machine that sync settings is never modified.

TBR=stevenjb@chromium.org
Review-Url: https://codereview.chromium.org/2289163003
Cr-Commit-Position: refs/heads/master@{#415748}
(cherry picked from commit a9c8ea0daf53303475b32177b76938cf6b31c04d)

Committed: https://chromium.googlesource.com/chromium/src/+/c952ec6aee549b6bc34bebc9a06c8392faf6d949

[Luis Héctor Chávez, 2016-09-02 23:09:28]

Description was changed from

==========
[Merge to M53]arc: Add arc enable sync pref initial set up.

Arc enable sync pref is false by default if user never modify sync settings.
This
patch enables arc sync service to start when user never manually modify sync
settings.

BUG=642907, http://b/31156650
TEST=Manual test on a machine that sync settings is never modified.

TBR=stevenjb@chromium.org
Review-Url: https://codereview.chromium.org/2289163003
Cr-Commit-Position: refs/heads/master@{#415748}
(cherry picked from commit a9c8ea0daf53303475b32177b76938cf6b31c04d)
==========

to

==========
[Merge to M53]arc: Add arc enable sync pref initial set up.

Arc enable sync pref is false by default if user never modify sync settings.
This
patch enables arc sync service to start when user never manually modify sync
settings.

BUG=642907, http://b/31156650
TEST=Manual test on a machine that sync settings is never modified.

TBR=stevenjb@chromium.org
Review-Url: https://codereview.chromium.org/2289163003
Cr-Commit-Position: refs/heads/master@{#415748}
(cherry picked from commit a9c8ea0daf53303475b32177b76938cf6b31c04d)

Committed:
https://chromium.googlesource.com/chromium/src/+/c952ec6aee549b6bc34bebc9a06c...
==========

[Luis Héctor Chávez, 2016-09-02 23:09:29]

Committed patchset #1 (id:1) manually as
c952ec6aee549b6bc34bebc9a06c8392faf6d949 (presubmit successful).