Disposing an OSR job should only restore the back edge state.

R=titzer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/24725002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16978 ce2b1a6d-e550-0410-aec6-3dcde31c8c00