Simplify test-mark-compact/NoPromotion test.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/42543008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17398 ce2b1a6d-e550-0410-aec6-3dcde31c8c00