Initial commit of profile guided optimization option

Initial commit of profile guided optimization option

FYI, instrumentation code that provides the orderfile is here: http://codereview.chromium.org/8770054/

BUG=chromiumos:20187
TEST=bootperf, see https://sites.google.com/a/google.com/chrome-msk/dev/boot-speed-up-effort

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=119073

[glotov, 2012-01-20 16:24:00]

Hi Dave! Please have a look at this tiny change.

[Nikita (slow), 2012-01-23 21:42:05]

Dave, ping

[DaveMoore, 2012-01-24 01:39:21]

lgtm