Fix LFastLiteral to check boilerplate elements kind.

Fix LFastLiteral to check boilerplate elements kind.

Adds a missing check that the elements kind of the boilerplate object
still has the expected elements kind, unoptimized code can transition
the boilerplate. Corner cases might cause the optimized code to be
reentered again.

R=danno@chromium.org
TEST=mjsunit/regress/regress-fast-literal-transition

Committed: https://code.google.com/p/v8/source/detail?r=11470

[danno, 2012-04-30 12:30:50]

lgtm