Don't set up an autorelease pool in ContentMainRunner on iOS

Don't set up an autorelease pool in ContentMainRunner on iOS

This causes crashes if the shutdown path is used on iOS, because on
iOS there's already a higher-level autorelease pool by the time this
code can be run.

BUG=None

Committed: https://crrev.com/839634ad8f32b814c2829d912bfb26b17fe03ac7
Cr-Commit-Position: refs/heads/master@{#314021}

[stuartmorgan, 2015-01-30 21:15:50]

stuartmorgan@chromium.org changed reviewers:
+ agl@chromium.org

[stuartmorgan, 2015-01-30 21:15:51]

This upstreams minor forking from the iOS tree.

[agl, 2015-01-30 21:32:21]

lgtm

[stuartmorgan, 2015-01-30 22:22:06]

The CQ bit was checked by stuartmorgan@chromium.org

[commit-bot: I haz the power, 2015-01-30 22:22:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/891843002/1

[commit-bot: I haz the power, 2015-01-30 23:14:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-30 23:15:32]

Patchset 1 (id:??) landed as
https://crrev.com/839634ad8f32b814c2829d912bfb26b17fe03ac7
Cr-Commit-Position: refs/heads/master@{#314021}