Motivation: we do not have test coverage for debuggersupport=off.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/256653004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20969 ce2b1a6d-e550-0410-aec6-3dcde31c8c00