This is to prepare for speculative concurrent OSR. I'm planning to add
another builtin to patch to, to indicate a concurrent OSR.

R=titzer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/23608004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16425 ce2b1a6d-e550-0410-aec6-3dcde31c8c00