with glib 2.36 and libsoup 2.42, ProxyResolverSoup is no longer needed. You can instead create a GSimpleProxyResolver (https://developer.gnome.org/gio/stable/GSimpleProxyResolver.html) and then set it as the SoupSession's :proxy-resolver property.
Closing this bug because the EFL port has been removed from trunk. If you feel this bug applies to a different upstream WebKit port and was closed in error, please either update the title and reopen the bug, or leave a comment to request this.