According to the spec, content from loopback addresses should no longer
be treated as mixed content even in secure origins. See:
- 349501cdaa
- https://w3c.github.io/webappsec-secure-contexts/#is-origin-trustworthy
Note that we only whitelist '127.0.0.1' and '::1' to match Chrome 53 and
later. See:
- 130ee686fa
It is unclear if HTTPS origins should be able to use workers and WebSocket
connections through a loopback HTTP address. They are not supported in Chrome
(whether this is intentional or not is uncertain) so lets just ignore them for
now.
See also: https://github.com/w3c/web-platform-tests/pull/5304
5e41427024