Fix bug in nextWeaker function of deltablue benchmark.

It does not seem to affect the correctness of the particular
workload it is currently running.

R=danno@chromium.org

Review URL: https://codereview.chromium.org/13994003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17399 ce2b1a6d-e550-0410-aec6-3dcde31c8c00