Only allow non-double if the observed representations are int32.

R=mvstanton@chromium.org

Review URL: https://chromiumcodereview.appspot.com/15988005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14852 ce2b1a6d-e550-0410-aec6-3dcde31c8c00