Revert r19409: "Allow ICs to be generated for own global proxy."

Causing Layout test crashes

TBR=verwaest@chromium.org

Review URL: https://codereview.chromium.org/170253002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19423 ce2b1a6d-e550-0410-aec6-3dcde31c8c00