Revert of Revert of Domain Reliability: Switch to BackoffEntry in Scheduler

Revert of Revert of Domain Reliability: Switch to BackoffEntry in Scheduler (patchset #1 id:1 of https://codereview.chromium.org/709333003/)

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

Original issue's description:
> 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}

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

Committed: https://crrev.com/390c0492512678b959a3ac1541cfec832ee3aec4
Cr-Commit-Position: refs/heads/master@{#303417}

[raymes, 2014-11-10 03:07:57]

Created Revert of Revert of Domain Reliability: Switch to BackoffEntry in
Scheduler

[commit-bot: I haz the power, 2014-11-10 03:08:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/681993003/1

[commit-bot: I haz the power, 2014-11-10 03:09:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-10 03:09:51]

Patchset 1 (id:??) landed as
https://crrev.com/390c0492512678b959a3ac1541cfec832ee3aec4
Cr-Commit-Position: refs/heads/master@{#303417}