IndexedDB: Enable leveldb log reuse on Chrome OS.

IndexedDB: Enable leveldb log reuse on Chrome OS.

Reuse was disabled in #317499 because CrOS corruption rates were spiking and
were too close to the stable branch point to gather more history.  Re-enabling
to allow monitoring in dev/beta channels with the hope that the rise we saw on
CrOS was normal fluctuations and unrelated to this change.

BUG=460568
Committed: https://crrev.com/319835313295e85743ad4f3e4f45af4595a53033
Cr-Commit-Position: refs/heads/master@{#321427}

[cmumford, 2015-03-19 18:07:14]

cmumford@chromium.org changed reviewers:
+ jsbell@chromium.org

[jsbell, 2015-03-19 18:41:26]

lgtm

[cmumford, 2015-03-19 18:50:40]

The CQ bit was checked by cmumford@chromium.org

[commit-bot: I haz the power, 2015-03-19 18:51:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1023773003/1

[commit-bot: I haz the power, 2015-03-19 20:42:41]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-19 20:43:36]

Patchset 1 (id:??) landed as
https://crrev.com/319835313295e85743ad4f3e4f45af4595a53033
Cr-Commit-Position: refs/heads/master@{#321427}