Sets site_for_cookies as the policy URL for same-site cookies for msg.
It is either the URL of the top-level document or null depending on whether
the registrable domain of this document's URL matches the registrable domain
of its parent's/opener's URL. For the top-level document it is set to the
document's URL.
Sets site_for_cookies as the policy URL for same-site cookies for msg.
It is either the URL of the top-level document or null depending on whether the registrable domain of this document's URL matches the registrable domain of its parent's/opener's URL. For the top-level document it is set to the document's URL.
See the same-site spec for more information.