Fix wrong DCHECK in Heap::FindAllocationMemento where bump pointer overflow points to the currently…

Fix wrong DCHECK in Heap::FindAllocationMemento where bump pointer overflow points to the currently used new space page.

BUG=chromium:501693
LOG=n

Committed: https://crrev.com/8b9924f6effaee83b437e2b9b19d81dbfc1d4f61
Cr-Commit-Position: refs/heads/master@{#29218}

[mvstanton, 2015-06-22 17:25:22]

mvstanton@chromium.org changed reviewers:
+ mvstanton@chromium.org

[mvstanton, 2015-06-22 17:25:22]

lgtm

[mvstanton, 2015-06-22 17:25:26]

The CQ bit was checked by mvstanton@chromium.org

[commit-bot: I haz the power, 2015-06-22 17:25:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1200833003/1

[commit-bot: I haz the power, 2015-06-22 17:28:06]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-22 17:28:07]

Try jobs failed on following builders:
  v8_presubmit on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_presubmit/builds/3612)

[Hannes Payer (out of office), 2015-06-22 18:45:14]

The CQ bit was checked by hpayer@chromium.org

[commit-bot: I haz the power, 2015-06-22 18:45:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1200833003/1

[commit-bot: I haz the power, 2015-06-22 18:53:25]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-22 18:53:27]

Try jobs failed on following builders:
  v8_presubmit on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_presubmit/builds/3625)

[Hannes Payer (out of office), 2015-06-23 08:55:09]

The CQ bit was checked by hpayer@chromium.org

[commit-bot: I haz the power, 2015-06-23 08:55:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1200833003/1

[commit-bot: I haz the power, 2015-06-23 09:07:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-23 09:07:41]

Patchset 1 (id:??) landed as
https://crrev.com/8b9924f6effaee83b437e2b9b19d81dbfc1d4f61
Cr-Commit-Position: refs/heads/master@{#29218}