Cleanup return values in SnapshotFileDetails

Cleanup return values in SnapshotFileDetails

This CL turns const by value return values into const by ref.

Replacing const value by a const ref when a member variable is safe, because
the member variable will live at least as long as the temporary object returned
now. It can also be more efficient, because returning a ref can spare copying.

BUG=393155
Committed: https://crrev.com/571b18256a44c782c1ac0c12bcaf13a73c0c497c
Cr-Commit-Position: refs/heads/master@{#299161}

[dvadym, 2014-10-10 11:27:13]

dvadym@chromium.org changed reviewers:
+ orenb@chromium.org

[dvadym, 2014-10-10 11:27:14]

Hi Oren,

 Could you please have a look?

Best regards,
Vadym

[Oren Blasberg, 2014-10-10 18:07:04]

lgtm

[Lei Zhang, 2014-10-10 18:35:32]

thestig@chromium.org changed reviewers:
+ thestig@chromium.org

[Lei Zhang, 2014-10-10 18:35:32]

The CQ bit was checked by thestig@chromium.org

[Lei Zhang, 2014-10-10 18:35:33]

lgtm

[commit-bot: I haz the power, 2014-10-10 18:36:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/646853003/1

[commit-bot: I haz the power, 2014-10-10 19:27:34]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-10 19:28:17]

Patchset 1 (id:??) landed as
https://crrev.com/571b18256a44c782c1ac0c12bcaf13a73c0c497c
Cr-Commit-Position: refs/heads/master@{#299161}