LazyInstance should be thread safe by default.

LazyInstance should be thread safe by default.

The only ways we use this class require it, as multiple isolates can race
to initialize data structures. This showed up as intermittant failures on
nosnap build bots.

R=hpayer@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=20794

[mvstanton, 2014-04-15 15:09:59]

Hi Hannes,
Here is one of the issues to address. PTAL, thx,
--Michael

ps - I think I see a comment to be removed.

[Hannes Payer (out of office), 2014-04-16 07:56:56]

https://codereview.chromium.org/238973004/diff/20001/src/lazy-instance.h
File src/lazy-instance.h (right):

https://codereview.chromium.org/238973004/diff/20001/src/lazy-instance.h#newc...
src/lazy-instance.h:178: // Thank you for making this the default, Satan.
Very entertaining, but we should probably not have Satan in our code base :)

[Hannes Payer (out of office), 2014-04-16 07:57:02]

lgtm

[mvstanton, 2014-04-16 11:31:49]

Committed patchset #2 manually as r20794 (presubmit successful).