[loggers] Guard object/code move events using mutexes.

[loggers] Guard object/code move events using mutexes.

Parallel compaction, i.e., concurrently moving of objects (and code) requires
proper synchronization in the logger.

R=hpayer@chromium.org
BUG=chromium:524425
LOG=N

Committed: https://crrev.com/8f403270670d03d86fc3ba49067e24287edd0d2c
Cr-Commit-Position: refs/heads/master@{#30714}

[Michael Lippautz, 2015-09-14 10:44:50]

mlippautz@chromium.org changed reviewers:
+ hpayer@chromium.org

[Michael Lippautz, 2015-09-14 10:44:50]

The first trivial spinoff from https://codereview.chromium.org/1330463002/
(prototype)

Parallel compaction requires concurrent logging of object and code move events.

[Hannes Payer (out of office), 2015-09-14 11:34:34]

lgtm

[Michael Lippautz, 2015-09-14 11:41:28]

The CQ bit was checked by mlippautz@chromium.org

[commit-bot: I haz the power, 2015-09-14 11:41:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1338253002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1338253002/1

[commit-bot: I haz the power, 2015-09-14 12:06:46]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-14 12:07:00]

Patchset 1 (id:??) landed as
https://crrev.com/8f403270670d03d86fc3ba49067e24287edd0d2c
Cr-Commit-Position: refs/heads/master@{#30714}