This optimization turns out to have a negative effect on i5 processors
throughout the board. This needs further investigation to figure out
the underlying reason but will be rolled out for now.

R=danno@chromium.org

Review URL: https://codereview.chromium.org/12388016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13772 ce2b1a6d-e550-0410-aec6-3dcde31c8c00