into heap snapshots non-HeapObjects. This is needed as a
preparation for adding DOM subtrees tracking.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/6596073

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7004 ce2b1a6d-e550-0410-aec6-3dcde31c8c00