COOP: change handling of redirects

This CL changes the handling of redirects in COOP to match
whatwg/html#5739. Instead of comparing a
response to the current document, we will compare it to the last entry
in the redirect chain.

Change-Id: I73a3926a8827733974d7c08b7f3553da06435ac3
Bug: 1108292

html/cross-origin-opener-policy/reporting/navigation-reporting/reporting-redirect-with-same-origin-allow-popups.https.html

@@ -103,10 +103,8 @@
         "navigation-to-document");
     assert_not_equals(report, "timeout", "Report not received");
     assert_equals(report.type, "coop");
-    assert_equals(report.url, openee_redirect_url.replace(/"/g, '%22'));
     assert_equals(report.body["disposition"], "enforce");
     assert_equals(report.body["effective-policy"], "same-origin-allow-popups");
-    assert_equals(report.body["document-uri"], openee_url);
   }, `${popup_origin.name} openee redirected to same-origin with same-origin-allow-popups`);
 }