Also, the name thread_local did not make much sense.

R=karlklose@chromium.org
BUG=1280

Review URL: http://codereview.chromium.org/6771003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7402 ce2b1a6d-e550-0410-aec6-3dcde31c8c00