Puts a check into the code flushing test to only perform this if the
flush_code flag is set to true. 


Review URL: http://codereview.chromium.org/2734006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4842 ce2b1a6d-e550-0410-aec6-3dcde31c8c00