Give the empty destination to the CORP check (#1531)

whatwg/fetch#1079 added the parameter to
the check. Here we provide the empty string, because request's
destination is not very meaningful here.

Author: yutakahirano

docs/index.bs

@@ -1875,7 +1875,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
                 1. [=list/For each=] |requestResponse| of |requestResponses|:
                     1. Add a copy of |requestResponse|'s response to |responses|.
             1. [=list/For each=] |response| of |responses|:
-                1. If |response|'s [=response/type=] is "`opaque`" and [=cross-origin resource policy check=] with |promise|'s [=relevant settings object=]'s [=environment settings object/origin=], |promise|'s [=relevant settings object=], and |response|'s [=internal/internal response=] returns <b>blocked</b>, then reject |promise| with a `TypeError` and abort these steps.
+                1. If |response|'s [=response/type=] is "`opaque`" and [=cross-origin resource policy check=] with |promise|'s [=relevant settings object=]'s [=environment settings object/origin=], |promise|'s [=relevant settings object=], "", and |response|'s [=internal/internal response=] returns <b>blocked</b>, then reject |promise| with a `TypeError` and abort these steps.
             1. [=Queue a task=], on |promise|'s [=relevant settings object=]'s [=responsible event loop=] using the [=DOM manipulation task source=], to perform the following steps:
                 1. Let |responseList| be a [=list=].
                 1. [=list/For each=] |response| of |responses|: