Use corresponding phi from the loop entry as a hint to infer proper representation for HUnkownOSRValue and dependent phis.

R=fschneider@chromium.org

Review URL: https://chromiumcodereview.appspot.com/9704012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11055 ce2b1a6d-e550-0410-aec6-3dcde31c8c00