When creating new windows/tabs from the content process, we currently choose
the default remote type based on the referrer URI, rather than the actual
remote type of the opener. While this generally works, it fails when opening
windows from URLs (particularly in iframes) which are opened in process types
other than their default process type, since the initial about:blank load gets
redirected to a new process before the child process has a chance to load its
actual target URI.
Using the actual remote type of the child opening the window fixes this
problem for URLs which are capable of being loaded into the child's process
type.
MozReview-Commit-ID: ClxVGxu52Lf
