Revert simplification of memory ordering that is causing TSAN errors.

Revert simplification of memory ordering that is causing TSAN errors.

Also added (unrelated) comment.

BUG=681349
Review-Url: https://codereview.chromium.org/2634093002
Cr-Commit-Position: refs/heads/master@{#443901}
Committed: https://chromium.googlesource.com/chromium/src/+/43c154f97c004706a96ed0f185d6232b12824c76

[bcwhite, 2017-01-16 14:04:56]

The CQ bit was checked by bcwhite@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-01-16 14:05:09]

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

[bcwhite, 2017-01-16 14:06:36]

Description was changed from

==========
Revert simplification of memory ordering that is causing TSAN errors.

BUG=681349
==========

to

==========
Revert simplification of memory ordering that is causing TSAN errors.

Also added (unrelated) comment.

BUG=681349
==========

[bcwhite, 2017-01-16 14:22:56]

bcwhite@chromium.org changed reviewers:
+ asvitkine@chromium.org

[commit-bot: I haz the power, 2017-01-16 15:03:39]

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

[commit-bot: I haz the power, 2017-01-16 15:03:39]

Dry run: This issue passed the CQ dry run.

[Alexei Svitkine (slow), 2017-01-16 15:41:30]

lgtm

[bcwhite, 2017-01-16 15:41:47]

The CQ bit was checked by bcwhite@chromium.org

[commit-bot: I haz the power, 2017-01-16 15:42:11]

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

[commit-bot: I haz the power, 2017-01-16 15:45:42]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1484581307250760, "parent_rev":
"6165c87433fd1016d114a1159780f6502c4ba798", "commit_rev":
"43c154f97c004706a96ed0f185d6232b12824c76"}

[commit-bot: I haz the power, 2017-01-16 15:46:16]

Description was changed from

==========
Revert simplification of memory ordering that is causing TSAN errors.

Also added (unrelated) comment.

BUG=681349
==========

to

==========
Revert simplification of memory ordering that is causing TSAN errors.

Also added (unrelated) comment.

BUG=681349

Review-Url: https://codereview.chromium.org/2634093002
Cr-Commit-Position: refs/heads/master@{#443901}
Committed:
https://chromium.googlesource.com/chromium/src/+/43c154f97c004706a96ed0f185d6...
==========

[commit-bot: I haz the power, 2017-01-16 15:46:17]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/43c154f97c004706a96ed0f185d6...