Remove promotion backup case and report OOM instead.

Remove promotion backup case and report OOM instead.

There are no test cases for this piece of code and it is really hard to test. If this rare case triggers, we are anyway in an OOM situation and would crash probably soon afterwards.

BUG=

Committed: https://crrev.com/e813afaf127ab80290153ab676dc07212bdc8946
Cr-Commit-Position: refs/heads/master@{#27026}

[Hannes Payer (out of office), 2015-03-04 13:20:58]

hpayer@chromium.org changed reviewers:
+ mstarzinger@chromium.org

[Michael Starzinger, 2015-03-04 14:33:56]

LGTM. We probably should watch the number of OOM's after this lands.

[Hannes Payer (out of office), 2015-03-05 18:01:25]

The CQ bit was checked by hpayer@chromium.org

[commit-bot: I haz the power, 2015-03-05 18:01:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/977013003/20001

[commit-bot: I haz the power, 2015-03-05 18:38:34]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-05 18:38:45]

Patchset 2 (id:??) landed as
https://crrev.com/e813afaf127ab80290153ab676dc07212bdc8946
Cr-Commit-Position: refs/heads/master@{#27026}

[ulan, 2015-04-01 15:37:22]

A revert of this CL (patchset #2 id:20001) has been created in
https://codereview.chromium.org/1050113002/ by ulan@chromium.org.

The reason for reverting is: Spike in OOM crashes: crbug.com/403113.