While allocating code objects, perform the incremental marking step before NULLing the new object. Otherwise the code cache cannot iterate the code space anymore, which is required to clear ICs.

Review URL: https://chromiumcodereview.appspot.com/10834408

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12345 ce2b1a6d-e550-0410-aec6-3dcde31c8c00