Revert of Domain Reliability: Switch to BackoffEntry in Scheduler

Revert of Domain Reliability: Switch to BackoffEntry in Scheduler (patchset #4 id:60001 of https://codereview.chromium.org/704893002/)

Reason for revert:
Speculative revert to attempt to fix https://code.google.com/p/chromium/issues/detail?id=431608

Original issue's description:
> Domain Reliability: Switch to BackoffEntry in Scheduler
>
> Previously, Domain Reliability was using homegrown backoff handling code.
> Switch to using the existing BackoffEntry.
>
> BUG=
>
> Committed: https://crrev.com/dd6819b1522473ae11b98cb60b8b613af01f4b56
> Cr-Commit-Position: refs/heads/master@{#303296}

TBR=davidben@chromium.org,ttuttle@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/ff48ecc9a42f24889384503488208db7b495f549
Cr-Commit-Position: refs/heads/master@{#303412}

[raymes, 2014-11-10 01:11:30]

Created Revert of Domain Reliability: Switch to BackoffEntry in Scheduler

[commit-bot: I haz the power, 2014-11-10 01:12:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/709333003/1

[commit-bot: I haz the power, 2014-11-10 01:13:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-10 01:14:08]

Patchset 1 (id:??) landed as
https://crrev.com/ff48ecc9a42f24889384503488208db7b495f549
Cr-Commit-Position: refs/heads/master@{#303412}

[raymes, 2014-11-10 03:07:56]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/681993003/ by raymes@chromium.org.

The reason for reverting is: This revert may have fixed this issue. Reverting to
see if the issue it re-appears without this..