This is needed so that HCompare, optimized for double inputs, works correctly on undefined inputs.
BUG=v8:1434
TEST=mjsunit/bugs/bug-1434.js

Review URL: http://codereview.chromium.org/7044049

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8237 ce2b1a6d-e550-0410-aec6-3dcde31c8c00