policy change.

I will put the changes back one at a time so we can see the effect of
them in isolation.  Also, there is a bug in the growth policy change
that I will fix before putting it back again.

Review URL: http://codereview.chromium.org/174050

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2712 ce2b1a6d-e550-0410-aec6-3dcde31c8c00