Enable system trace clock use on chrome os.

Enable system trace clock use on chrome os.

Manually define CLOCK_SYSTEM_TRACE for OS_CHROMEOS.  This is  in the code (and not gyp) to minimize scope.

BUG=chromium-os:30502
TEST=verify chrome:tracing works w/ a chromeos=1 build on linux and on cros (using the correct clock in each case)

Change-Id: I9439a1de9fe30cb2f34652020a29a4450b71e1ea


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=136389

[willchan no longer on Chromium, 2012-05-05 19:39:52]

Sorry Sam, I forget the reasoning why I suggested this location. Can you remind
me why I didn't suggest you use #if defined(OS_CHROME) within the .cc file that
needs it?

[Sam Leffler, 2012-05-07 17:11:01]

You suggested base.gypi to minimize the scope of the #define.  I was trying to
not pollute the .cc file because I want to (eventually) surface it in the system
include files but that's proven difficult.  FWIW the way it's enabled in the
code now is w/ defined(OS_POSIX) (to check for support for clock_gettime) and
then defined(CLOCK_SYSTEM_TRACE) to check for support for the specific clock.  I
didn't use defined(OS_CHROMEOS) because I'm trying to upstream to linux but can
certainly change to that.

[Sam Leffler, 2012-05-07 21:29:06]

PTAL; this was working previously because of changes in my chroot that made
builds work; verified this change against a pristine chroot and also against
build outside the chroot (for chrome on linux w/ chromeos=1 case)

can still move #define to be in code if prefered

[willchan no longer on Chromium, 2012-05-07 21:35:44]

Let's move it to the .cc file first and then the gyp file later if
necessary.

On Mon, May 7, 2012 at 2:29 PM, <sleffler@chromium.org> wrote:

> PTAL; this was working previously because of changes in my chroot that made
> builds work; verified this change against a pristine chroot and also
> against
> build outside the chroot (for chrome on linux w/ chromeos=1 case)
>
> can still move #define to be in code if prefered
>
>
http://codereview.chromium.**org/10356028/<http://codereview.chromium.org/103...
>

[Sam Leffler, 2012-05-08 17:47:06]

PTAL

[willchan no longer on Chromium, 2012-05-09 01:44:46]

lgtm

[willchan no longer on Chromium, 2012-05-09 01:45:14]

Oh, please update the CL description too, and include the rational behind the
choice to do this in the .cc file.

[commit-bot: I haz the power, 2012-05-10 15:45:19]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/sleffler@chromium.org/10356028/8001

[commit-bot: I haz the power, 2012-05-10 18:45:20]

Try job failure for 10356028-8001 (retry) on win_rel for step "browser_tests".
It's a second try, previously, step "browser_tests" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2012-05-10 18:52:28]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/sleffler@chromium.org/10356028/8001

[commit-bot: I haz the power, 2012-05-10 21:10:55]

Change committed as 136389