Also cleans up some uninitialized data I saw while investigating
the problem.

R=jkummerow@chromium.org, machenbach@chromium.org

Review URL: https://codereview.chromium.org/23119004

Patch from Ken Mixter <kmixter@google.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16235 ce2b1a6d-e550-0410-aec6-3dcde31c8c00