Releasing context handle is not enough to release context, it might be indirectly reachable through compilation cache.

TBR=sgjesse@chromium.org

Review URL: http://codereview.chromium.org/3750017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5652 ce2b1a6d-e550-0410-aec6-3dcde31c8c00