Fix gcstress test failure

Fix gcstress test failure

Map collection complicates a test that wants to assert on code opt/deopt
because of prototype-chain changes. It can happen that a gc occurs
in the stack guard at the start of optimized function foo that deopts
function foo because of a map being collected and deoptimizing it's
dependent code.

R=bmeurer@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=19258

[mvstanton, 2014-02-11 08:57:36]

Hi Benedikt, PTAL, thx!
--Michael

[Benedikt Meurer, 2014-02-11 09:00:14]

LGTM, nice debugging! :-)

[mvstanton, 2014-02-11 09:06:19]

Committed patchset #1 manually as r19258 (presubmit successful).