Fix race in INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO

Fix race in INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO

BUG=webrtc:7251
Review-Url: https://codereview.webrtc.org/2716343002
Cr-Commit-Position: refs/heads/master@{#16862}
Committed: https://chromium.googlesource.com/external/webrtc/+/055ecd1fdfbe39c62df071c81bd210cd74559993

[tommi, 2017-02-27 12:07:20]

The CQ bit was checked by tommi@webrtc.org to run a CQ dry run

[commit-bot: I haz the power, 2017-02-27 12:07:30]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[tommi, 2017-02-27 12:07:47]

tommi@webrtc.org changed reviewers:
+ sprang@webrtc.org

[sprang_webrtc, 2017-02-27 12:09:23]

Tested manually.
lgtm

[commit-bot: I haz the power, 2017-02-27 12:49:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-02-27 12:50:00]

Dry run: This issue passed the CQ dry run.

[tommi, 2017-02-27 13:05:35]

The CQ bit was checked by tommi@webrtc.org

[commit-bot: I haz the power, 2017-02-27 13:05:45]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2017-02-27 13:09:06]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1488200735717270, "parent_rev":
"19854a0053d177d817b5827cba879fe43c22bf20", "commit_rev":
"055ecd1fdfbe39c62df071c81bd210cd74559993"}

[commit-bot: I haz the power, 2017-02-27 13:09:08]

Description was changed from

==========
Fix race in INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO

BUG=webrtc:7251
==========

to

==========
Fix race in INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO

BUG=webrtc:7251

Review-Url: https://codereview.webrtc.org/2716343002
Cr-Commit-Position: refs/heads/master@{#16862}
Committed:
https://chromium.googlesource.com/external/webrtc/+/055ecd1fdfbe39c62df071c81...
==========

[commit-bot: I haz the power, 2017-02-27 13:09:10]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/external/webrtc/+/055ecd1fdfbe39c62df071c81...