Proactively ensure that that objects don't get FAST_DOUBLE_ELEMENTS to reduce the number of double boxing operations when generated code calls the runtime frequently to satisfy KeyedLoad requests.

Review URL: http://codereview.chromium.org/8416014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9833 ce2b1a6d-e550-0410-aec6-3dcde31c8c00