- if value is a result of integer32 to double conversion (can't be NaN);

- if value was loaded from fast double backing store (already canonicalized).

R=danno@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10054009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11278 ce2b1a6d-e550-0410-aec6-3dcde31c8c00