Since we have an issue with code flusing on the trybots preventing us
from pushing to chromium, a new flag for enabling code flushing,
--flush_code, is introduced with this change (defaulting to false).

Review URL: http://codereview.chromium.org/2734005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4840 ce2b1a6d-e550-0410-aec6-3dcde31c8c00