IPC: Fix size_t to int cast for Win64 build.

IPC: Fix size_t to int cast for Win64 build.

BUG=
TBR=cpu@chromium.org
NOTRY=true

No try as this is blocking the Win64 build.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=258456

[epennerAtGoogle, 2014-03-20 20:45:05]

Ptal.

This target isn't on Win64 bots so a compiler warning slipped in. I'm TBR'ing
since this is just a compiler warning on a test.

[epenner, 2014-03-20 20:46:55]

The CQ bit was checked by epenner@chromium.org

[commit-bot: I haz the power, 2014-03-20 20:48:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/epenner@chromium.org/206853002/1

[Will Harris, 2014-03-20 20:53:44]

LGTM

[cpu_(ooo_6.6-7.5), 2014-03-20 22:37:29]

lgtm

[commit-bot: I haz the power, 2014-03-20 23:10:06]

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

[commit-bot: I haz the power, 2014-03-20 23:10:07]

Retried try job too often on win_rel for step(s) unit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[epenner, 2014-03-20 23:32:11]

The CQ bit was checked by epenner@chromium.org

[commit-bot: I haz the power, 2014-03-20 23:34:18]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/epenner@chromium.org/206853002/1

[commit-bot: I haz the power, 2014-03-20 23:36:26]

Change committed as 258456