d8: Leak context_mutex_ so it will never be destroyed while locked

d8: Leak context_mutex_ so it will never be destroyed while locked

Calling quit() from d8 will call exit(), which will run static destructors. If
context_mutex_ is statically allocated, pthread_mutex_destroy will be called.

When running d8 in "isolates" mode, another thread may be running. If it calls
CreateEvaluationContext, it will lock the context_mutex_. If the mutex is
destroyed while it is locked, it will return an error.

This CL changes the Mutex to a LazyMutex, which will leak instead of being
destroyed.

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

Committed: https://crrev.com/162f116a913058cb02f0e5fe1becf7c11d1db56b
Cr-Commit-Position: refs/heads/master@{#29709}

[Jarin, 2015-07-16 09:42:11]

lgtm.

[Michael Achenbach, 2015-07-16 12:54:13]

lgtm

[binji, 2015-07-16 16:38:38]

The CQ bit was checked by binji@chromium.org

[commit-bot: I haz the power, 2015-07-16 16:39:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1240553003/1

[commit-bot: I haz the power, 2015-07-16 16:40:44]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-16 16:41:01]

Patchset 1 (id:??) landed as
https://crrev.com/162f116a913058cb02f0e5fe1becf7c11d1db56b
Cr-Commit-Position: refs/heads/master@{#29709}