Fix crash in debug builds introduced with r21110.

Fix crash in debug builds introduced with r21110.

Basically we should not check for map deprecation during
code selection, because that may run on the concurrent
compiler thread. So the fix is to move this logic to the
code generation phase instead, which is always run on the
main thread.

R=mvstanton@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21112

[Benedikt Meurer, 2014-05-02 07:50:27]

Hey Michael,
Here's the fix for the debug crash introduced with my last CL. As discussed
offline, it just moves the logic from code selection to code generation, where
it's always safe to check map deprecation status.
PTAL
-- Benedikt

[mvstanton, 2014-05-02 07:53:38]

lgtm

[Benedikt Meurer, 2014-05-02 08:08:39]

Committed patchset #1 manually as r21112 (presubmit successful).