Since we don't have a full-codegen compiler anymore, we no longer
generate Code::FUNCTION kind. Nice! Here is some cleanup.

Bug: v8:6409
Change-Id: I05634e4ca85c4037b49a4346f4e8bae8042b8762
Reviewed-on: https://chromium-review.googlesource.com/657817
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47951}