Quota: Clean up (Client)UsageTracker

Quota: Clean up (Client)UsageTracker

- Remove unnecessary indirect callback
- Replace traditional for-loops with range-based for-loops

BUG=n/a
TEST=should pass all existing tests (no behavioral changes)

Committed: https://crrev.com/fba2bd6ec5c9767edccc51bd5f732fec9e3ae978
Cr-Commit-Position: refs/heads/master@{#303605}

[nhiroki, 2014-11-11 05:15:28]

Patchset #1 (id:1) has been deleted

[nhiroki, 2014-11-11 05:15:50]

nhiroki@chromium.org changed reviewers:
+ tzik@chromium.org

[nhiroki, 2014-11-11 05:15:51]

PTAL

[tzik, 2014-11-11 05:41:18]

lgtm

[nhiroki, 2014-11-11 05:44:03]

The CQ bit was checked by nhiroki@chromium.org

[commit-bot: I haz the power, 2014-11-11 05:44:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/715763002/20001

[commit-bot: I haz the power, 2014-11-11 07:45:40]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2014-11-11 07:46:45]

Patchset 1 (id:??) landed as
https://crrev.com/fba2bd6ec5c9767edccc51bd5f732fec9e3ae978
Cr-Commit-Position: refs/heads/master@{#303605}