Make sure builtin code objects get their builtin tags
first. Otherwise a particular JSFunction object could set
its custom name to a generic builtin.

LOG=N
R=ulan@chromium.org, yurys@chromium.org

Review URL: https://codereview.chromium.org/145973006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18926 ce2b1a6d-e550-0410-aec6-3dcde31c8c00