Fix race condition with PendingSpawnQueue in ChildProcessLauncher

Fix race condition with PendingSpawnQueue in ChildProcessLauncher

As explained in crbug.com/585952#c7, lack of synchronization between updates
of allocators' free slots and the pending queue can lead a race resulting
in a pending spawn being stuck in the queue forewer.

This issue has been revealed by WebView's testCreateLoadDestroyManyTimes in
the sandboxed renderer mode.

BUG=429657, 585952
Committed: https://crrev.com/7a7eeabbb31ccba00bb951a8f7708462b424f4e3
Cr-Commit-Position: refs/heads/master@{#376060}

[mnaganov (inactive), 2016-02-12 21:36:35]

mnaganov@chromium.org changed reviewers:
+ jaekyun@chromium.org

[mnaganov (inactive), 2016-02-12 21:36:36]

Hi Jaekyin, PTAL at the patch!

[Jaekyun Seok (inactive), 2016-02-14 22:12:43]

jaekyun@chromium.org changed reviewers:
+ aelias@chromium.org

[Jaekyun Seok (inactive), 2016-02-14 22:12:43]

lgtm, but I'm working in the Clank team anymore.

Alex, could you please take a look at this CL?

[mnaganov (inactive), 2016-02-17 17:25:15]

mnaganov@chromium.org changed reviewers:
+ dtrainor@chromium.org
- aelias@chromium.org

[mnaganov (inactive), 2016-02-17 17:25:15]

Alex is on vacation. David, would you be so kind to take a look?

[David Trainor- moved to gerrit, 2016-02-17 21:57:47]

lgtm

[mnaganov (inactive), 2016-02-18 00:41:41]

The CQ bit was checked by mnaganov@chromium.org

[commit-bot: I haz the power, 2016-02-18 00:43:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1695723004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1695723004/1

[commit-bot: I haz the power, 2016-02-18 01:55:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-02-18 01:56:33]

Description was changed from

==========
Fix race condition with PendingSpawnQueue in ChildProcessLauncher

As explained in crbug.com/585952#c7, lack of synchronization between updates
of allocators' free slots and the pending queue can lead a race resulting
in a pending spawn being stuck in the queue forewer.

This issue has been revealed by WebView's testCreateLoadDestroyManyTimes in
the sandboxed renderer mode.

BUG=429657,585952
==========

to

==========
Fix race condition with PendingSpawnQueue in ChildProcessLauncher

As explained in crbug.com/585952#c7, lack of synchronization between updates
of allocators' free slots and the pending queue can lead a race resulting
in a pending spawn being stuck in the queue forewer.

This issue has been revealed by WebView's testCreateLoadDestroyManyTimes in
the sandboxed renderer mode.

BUG=429657,585952

Committed: https://crrev.com/7a7eeabbb31ccba00bb951a8f7708462b424f4e3
Cr-Commit-Position: refs/heads/master@{#376060}
==========

[commit-bot: I haz the power, 2016-02-18 01:56:34]

Patchset 1 (id:??) landed as
https://crrev.com/7a7eeabbb31ccba00bb951a8f7708462b424f4e3
Cr-Commit-Position: refs/heads/master@{#376060}