Bug 1534681 Use ReferrerInfo class in document r=ckerschb,baku,Gijs

Also, in many place, we use document uri as referrer. It is not right
for the case srdoc iframe. We should use the last non-srdoc parent
document's uri

Differential Revision: https://phabricator.services.mozilla.com/D30191

dom/xhr/XMLHttpRequestMainThread.cpp

@@ -2005,7 +2005,9 @@ XMLHttpRequestMainThread::OnStartRequest(nsIRequest* request) {
     NS_ENSURE_SUCCESS(rv, rv);
 
     // the spec requires the response document.referrer to be the empty string
-    mResponseXML->SetReferrer(NS_LITERAL_CSTRING(""));
+    nsCOMPtr<nsIReferrerInfo> referrerInfo =
+        new ReferrerInfo(nullptr, true, mResponseXML->GetReferrerPolicy());
+    mResponseXML->SetReferrerInfo(referrerInfo);
 
     mXMLParserStreamListener = listener;
     rv = mXMLParserStreamListener->OnStartRequest(request);