Port r9870 (959ec43).

Original commit message:

This depends on
http://codereview.chromium.org/8352039 and
http://codereview.chromium.org/8423005 .

BUG=
TEST=

Review URL: http://codereview.chromium.org/8467007
Patch from Gergely Kis <gergely@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9887 ce2b1a6d-e550-0410-aec6-3dcde31c8c00