This removes the FACTORY helper macro to avoid accidental TLS access
when using the factory. Most internal code has access to the Isolate by
now whereas tests which are not performance critical still heavily use
TLS access through explicit Isolate::Current() calls.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/16337005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14931 ce2b1a6d-e550-0410-aec6-3dcde31c8c00