d8 workers: make sure Shell::Quit is only called once

d8 workers: make sure Shell::Quit is only called once

When running with isolates, Quit can be called simultaneously by two threads.
If this happens, then both threads try to clean up the Workers, which could
crash.

BUG=v8:4279
R=jarin@chromium.org
R=machenbach@chromium.org
LOG=n

Committed: https://crrev.com/76184292b392d107609f21662a949b58bb1e258c
Cr-Commit-Position: refs/heads/master@{#29654}

[Jarin, 2015-07-14 04:54:00]

lgtm.

Even though it might be better to put the 'once' variable on the Shell class
(the Chrome build likes to complain about static initialization).

[Michael Achenbach, 2015-07-14 08:47:43]

lgtm

[binji, 2015-07-14 16:27:47]

On 2015/07/14 at 04:54:00, jarin wrote:
> lgtm.
> 
> Even though it might be better to put the 'once' variable on the Shell class
(the Chrome build likes to complain about static initialization).

Should be OK: OnceType is an alias for AtomicWord. That being said, if it had a
constructor it would be problematic; GCC adds guards for threadsafe function
statics, but I'm not sure about other compilers pre-C++11.

Anyway, I've moved it out to make it clearer.

[binji, 2015-07-14 16:41:26]

The CQ bit was checked by binji@chromium.org

[binji, 2015-07-14 16:41:26]

The patchset sent to the CQ was uploaded after l-g-t-m from jarin@chromium.org,
machenbach@chromium.org
Link to the patchset: https://codereview.chromium.org/1230403003/#ps60001
(title: "remove function static")

[commit-bot: I haz the power, 2015-07-14 16:41:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1230403003/60001

[commit-bot: I haz the power, 2015-07-14 17:03:58]

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

[commit-bot: I haz the power, 2015-07-14 17:03:58]

Try jobs failed on following builders:
  v8_win_nosnap_shared_compile_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_win_nosnap_shared_compil...)

[binji, 2015-07-14 17:11:06]

The CQ bit was checked by binji@chromium.org

[binji, 2015-07-14 17:11:06]

The patchset sent to the CQ was uploaded after l-g-t-m from jarin@chromium.org,
machenbach@chromium.org
Link to the patchset: https://codereview.chromium.org/1230403003/#ps80001
(title: "move once_type_ out of V8_SHARED section")

[commit-bot: I haz the power, 2015-07-14 17:11:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1230403003/80001

[commit-bot: I haz the power, 2015-07-14 17:42:12]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-07-14 17:42:23]

Patchset 5 (id:??) landed as
https://crrev.com/76184292b392d107609f21662a949b58bb1e258c
Cr-Commit-Position: refs/heads/master@{#29654}

[binji, 2015-07-14 18:09:33]

A revert of this CL (patchset #5 id:80001) has been created in
https://codereview.chromium.org/1235083004/ by binji@chromium.org.

The reason for reverting is: Breaks webkit_unit_tests. See
http://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Win/builds/853/....