As most of call IC code is tied to a context anyway we can save a few dependent loads by having a direct reference to an initial map of a global function.

Review URL: http://codereview.chromium.org/2239009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4802 ce2b1a6d-e550-0410-aec6-3dcde31c8c00