Port r11470 (621f96c0)

Original commit message:
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.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10271018
Patch from Akos Palfi <palfia@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11474 ce2b1a6d-e550-0410-aec6-3dcde31c8c00