This is a step in the direction of disentangling all uses of SetOwnPropertyIgnoreAttributes so we can provide a more specific implementation for those usecases, and reduce the capabilities of those clients, avoiding subtle bugs.

InitializeProperty only supports adding properties to extensible objects that do not contain the property yet. JSGlobalProxies cannot have properties themselves, so are not supported either.

BUG=
R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/352813002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22095 ce2b1a6d-e550-0410-aec6-3dcde31c8c00