Finish TODO in Schedule. s/entry/start/g and s/exit/end/g to be more regular.

R=jarin@chromium.org
BUG=

Review URL: https://codereview.chromium.org/484653002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23161 ce2b1a6d-e550-0410-aec6-3dcde31c8c00