mac/rlz: Correctly check for fd existence

mac/rlz: Correctly check for fd existence

Found while looking at this file for http://crbug.com/143950, but
I don't think this causes that bug.

BUG=143950
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=152616

[Nico, 2012-08-21 18:25:36]

This would only be an issue if the lock gets fd 0 (since closing fd -1 should be
harmless)), but we don't close 0 in chrome, so that shouldn't happen.

[Mark Mentovai, 2012-08-21 18:27:59]

LGTM

[commit-bot: I haz the power, 2012-08-21 18:36:53]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/thakis@chromium.org/10827449/1

[commit-bot: I haz the power, 2012-08-21 19:57:53]

Try job failure for 10827449-1 (retry) on mac_rel for step "browser_tests".
It's a second try, previously, step "browser_tests" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...