Currently only the DocumentPrincipal and StoragePrincipal (which is either the document's principal or the partitioned principal) are exposed on WindowGlobalParent. These are generally the most useful flags, but sometimes you need the raw partitioned principal. This patch simplifies the setup by sending down the partitioned principal when requested, and using a boolean flag to track which principal should be used as the storage principal. Differential Revision: https://phabricator.services.mozilla.com/D293366