Fix shutdown performance metrics gathering to work on ARM.
Fix shutdown performance metrics gathering to work on ARM.

BUG=chromium-os:14121
TEST=platform_Shutdown

Review URL: http://codereview.chromium.org/6881017

Change-Id: Iac019721a26dcfbd39d8038ca4e28f3b28d74fc4

joshfire/chromiumos-platform-init