Remove obsolete debug code and add new one.

This removes obsolete debugging code that was added to flush out
problems with the code flusher. It also add new debugging code to
flush out problems with code entry slot recording.

R=hpayer@chromium.org
BUG=chromium:168582

Review URL: https://codereview.chromium.org/12088106

git-svn-id: https://v8.googlecode.com/svn/trunk@13577 ce2b1a6d-e550-0410-aec6-3dcde31c8c00