Serializer: assert that we deserialize only one native context.

Serializer: assert that we deserialize only one native context.

R=mvstanton@chromium.org
NOTRY=true

Committed: https://crrev.com/cc9da821eac3d1cecb46149c00cb364efd426bcf
Cr-Commit-Position: refs/heads/master@{#27932}

[Yang, 2015-04-20 08:54:55]

The CQ bit was checked by yangguo@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-04-20 08:55:22]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1097893002/1

[mvstanton, 2015-04-20 09:06:12]

lgtm

[commit-bot: I haz the power, 2015-04-20 09:36:16]

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

[commit-bot: I haz the power, 2015-04-20 09:36:17]

Dry run: Try jobs failed on following builders:
  v8_linux64_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_rel/builds/5010)

[Yang, 2015-04-20 09:56:52]

The CQ bit was checked by yangguo@chromium.org

[commit-bot: I haz the power, 2015-04-20 09:57:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1097893002/1

[commit-bot: I haz the power, 2015-04-20 09:57:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-20 09:57:30]

Patchset 1 (id:??) landed as
https://crrev.com/cc9da821eac3d1cecb46149c00cb364efd426bcf
Cr-Commit-Position: refs/heads/master@{#27932}