Increase final idle time in idle notifcation of test test-api/Regress2107.

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/653863002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24579 ce2b1a6d-e550-0410-aec6-3dcde31c8c00