Move WriteJSONFile to its sole caller's package, with some refactoring.

Move WriteJSONFile to its sole caller's package, with some refactoring.

BUG=732677
Review-Url: https://codereview.chromium.org/2938823003
Committed: https://github.com/luci/luci-go/commit/3b2cf368c09e435c41d69235e93ff7eb5980bd5b

[mcgreevy, 2017-06-15 05:09:41]

mcgreevy@chromium.org changed reviewers:
+ tansell@chromium.org

[mithro, 2017-06-15 05:16:19]

lgtm

[mcgreevy, 2017-06-15 05:19:50]

The CQ bit was checked by mcgreevy@chromium.org

[commit-bot: I haz the power, 2017-06-15 05:19:56]

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, 2017-06-15 05:30:27]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1497503990354300, "parent_rev":
"a4a9617ec3dc88d18d92653b0270f584fcbcc98e", "commit_rev":
"3b2cf368c09e435c41d69235e93ff7eb5980bd5b"}

[commit-bot: I haz the power, 2017-06-15 05:30:30]

Description was changed from

==========
Move WriteJSONFile to its sole caller's package, with some refactoring.

BUG=732677
==========

to

==========
Move WriteJSONFile to its sole caller's package, with some refactoring.

BUG=732677

Review-Url: https://codereview.chromium.org/2938823003
Committed:
https://github.com/luci/luci-go/commit/3b2cf368c09e435c41d69235e93ff7eb5980bd5b
==========

[commit-bot: I haz the power, 2017-06-15 05:30:31]

Committed patchset #1 (id:1) as
https://github.com/luci/luci-go/commit/3b2cf368c09e435c41d69235e93ff7eb5980bd5b