Movef a helper class to the top level to avoid
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40145.

TBR=ulan@chromium.org

Review URL: https://codereview.chromium.org/11194050

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12751 ce2b1a6d-e550-0410-aec6-3dcde31c8c00