After the changes in this bug, about:blank loads triggered by chrome will
finish in a "web" content process, as they have an untrusted null principal
without a precursor. In a few places throughout the codebase, however, we
perform about:blank loads with the explicit expectation that they do not change
processes. This new remoteTypeOverride option allows the intended final process
to be explicitly specified in this situation.
For security & simplicity reasons, this new attribute is limited to only be
usable on system-principal triggered loads of about:blank in toplevel browsing
contexts.
Differential Revision: https://phabricator.services.mozilla.com/D120671
e836c49649