Avoid threading races on TraceSamplingThread's members

Avoid threading races on TraceSamplingThread's members

The original CL was landed in https://codereview.chromium.org/26541005/
but the CL caused a dead lock. This CL fixed the issue.

NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=233266

[haraken, 2013-10-18 08:58:54]

I reverted https://codereview.chromium.org/26541005/ because the CL caused a
dead lock.

This CL addresses the issue. PTAL.

[dsinclair, 2013-10-18 15:17:53]

lgtm

[Xianzhu, 2013-10-18 16:24:53]

lgtm

[nduca, 2013-10-23 07:06:02]

lgtm

[haraken, 2013-10-28 01:54:46]

Sorry for being late.

https://codereview.chromium.org/28593003/diff/1/base/debug/trace_event_impl.cc
File base/debug/trace_event_impl.cc (right):

https://codereview.chromium.org/28593003/diff/1/base/debug/trace_event_impl.c...
base/debug/trace_event_impl.cc:835: WaitableEvent* waitable_event_for_testing_;

I noticed this doesn't fix threading races. We have to change WaitableEvent* to
WaitableEvent to avoid races. I fixed it in patch set 3. PTAL again.

[commit-bot: I haz the power, 2013-11-06 12:58:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/haraken@chromium.org/28593003/120001

[commit-bot: I haz the power, 2013-11-06 13:22:21]

Retried try job too often on chromium_presubmit for step(s) presubmit
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=chromium_p...

[commit-bot: I haz the power, 2013-11-06 13:57:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/haraken@chromium.org/28593003/120001

[commit-bot: I haz the power, 2013-11-06 14:00:04]

Change committed as 233266