This change results in less scan on scavenge memory chunks.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/15896037

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15037 ce2b1a6d-e550-0410-aec6-3dcde31c8c00