Fix typer to actually visit the entire graph.

R=titzer@chromium.org
TEST=mjsunit

Review URL: https://codereview.chromium.org/545223002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23740 ce2b1a6d-e550-0410-aec6-3dcde31c8c00