AllocationSite is now checked to be sure a valid Site goes in.
This is temporary code to diagnose chromium bug 284577.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/23622029

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16705 ce2b1a6d-e550-0410-aec6-3dcde31c8c00