Fix to the GCM Account Tracker flooding on a stale refresh token

Fix to the GCM Account Tracker flooding on a stale refresh token

As a solution to a problem the Account Tracker will assume a stale
refresh token when it cannot get access token. Backoff logic in
token fetcher handles the case where service might not be reachale
and situations like that.

If the user signs in properly the account will be re-added.

BUG=452131
R=zea@chromium.org,dimich@chromium.org

Committed: https://crrev.com/be981e7796e29eba1ab9c6e7c65d1c56b0840b5f
Cr-Commit-Position: refs/heads/master@{#313136}

[Nicolas Zea, 2015-01-26 19:54:21]

lgtm

[fgorski, 2015-01-26 20:40:07]

The CQ bit was checked by fgorski@chromium.org

[commit-bot: I haz the power, 2015-01-26 20:41:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/878713002/1

[commit-bot: I haz the power, 2015-01-26 21:07:46]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-26 21:08:51]

Patchset 1 (id:??) landed as
https://crrev.com/be981e7796e29eba1ab9c6e7c65d1c56b0840b5f
Cr-Commit-Position: refs/heads/master@{#313136}