Skip toString-number webkit test because of spurious failure.

BUG=
R=machenbach@chromium.org

Review URL: https://codereview.chromium.org/439933006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22886 ce2b1a6d-e550-0410-aec6-3dcde31c8c00