This CL constitutes the invariant that the top pointer in new space is always larger than objects allocated since the last new space garbage collection.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/26865004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17185 ce2b1a6d-e550-0410-aec6-3dcde31c8c00