this is implemented for intel platforms only, as they are the only ones which show speed up with this change

R=svenpanne@chromium.org
BUG=

Review URL: https://codereview.chromium.org/48303002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17903 ce2b1a6d-e550-0410-aec6-3dcde31c8c00