Add function document, and small refactor around Start/StopArc().

Add function document, and small refactor around Start/StopArc().

This CL has several minor refactoring.
- Add function comments to StartArc(), StopArc() and OnProvisioningFinished().
- Moved StartArc() and StopArc() into private.
- Introduced StartArcForTesting() proxy only for testing purpose.
- Reorder StartArc() and StopArc() in .cc file.

BUG=n/a
TEST=Ran bots.

Review-Url: https://codereview.chromium.org/2722263002
Cr-Commit-Position: refs/heads/master@{#454166}
Committed: https://chromium.googlesource.com/chromium/src/+/0e38d14cf1c750b1c7984b2d0b30c12b4f8470ff

[hidehiko, 2017-03-01 19:11:48]

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

[commit-bot: I haz the power, 2017-03-01 19:12:11]

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

[hidehiko, 2017-03-01 19:13:50]

hidehiko@chromium.org changed reviewers:
+ yusukes@chromium.org

[hidehiko, 2017-03-01 19:13:51]

Yusuke-san, let me address your comments for
https://codereview.chromium.org/2723073002/, here.

PTAL.

[commit-bot: I haz the power, 2017-03-01 19:41:56]

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

[commit-bot: I haz the power, 2017-03-01 19:41:57]

Dry run: This issue passed the CQ dry run.

[Yusuke Sato, 2017-03-01 19:46:41]

lgtm, thanks!

[hidehiko, 2017-03-02 01:45:56]

The CQ bit was checked by hidehiko@chromium.org

[commit-bot: I haz the power, 2017-03-02 01:46:56]

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, 2017-03-02 02:00:56]

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

[commit-bot: I haz the power, 2017-03-02 02:00:57]

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

[hidehiko, 2017-03-02 02:26:55]

The CQ bit was checked by hidehiko@chromium.org

[hidehiko, 2017-03-02 02:26:55]

The patchset sent to the CQ was uploaded after l-g-t-m from yusukes@chromium.org
Link to the patchset: https://codereview.chromium.org/2722263002/#ps20001
(title: "Rebase")

[commit-bot: I haz the power, 2017-03-02 02:27:44]

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, 2017-03-02 03:39:41]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1488421615068320,
"parent_rev": "9bcb0bd7cd927a70d47c983fbd071ccf6cdded58", "commit_rev":
"0e38d14cf1c750b1c7984b2d0b30c12b4f8470ff"}

[commit-bot: I haz the power, 2017-03-02 03:40:40]

Description was changed from

==========
Add function document, and small refactor around Start/StopArc().

This CL has several minor refactoring.
- Add function comments to StartArc(), StopArc() and OnProvisioningFinished().
- Moved StartArc() and StopArc() into private.
- Introduced StartArcForTesting() proxy only for testing purpose.
- Reorder StartArc() and StopArc() in .cc file.

BUG=n/a
TEST=Ran bots.
==========

to

==========
Add function document, and small refactor around Start/StopArc().

This CL has several minor refactoring.
- Add function comments to StartArc(), StopArc() and OnProvisioningFinished().
- Moved StartArc() and StopArc() into private.
- Introduced StartArcForTesting() proxy only for testing purpose.
- Reorder StartArc() and StopArc() in .cc file.

BUG=n/a
TEST=Ran bots.

Review-Url: https://codereview.chromium.org/2722263002
Cr-Commit-Position: refs/heads/master@{#454166}
Committed:
https://chromium.googlesource.com/chromium/src/+/0e38d14cf1c750b1c7984b2d0b30...
==========

[commit-bot: I haz the power, 2017-03-02 03:40:41]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/chromium/src/+/0e38d14cf1c750b1c7984b2d0b30...