Use AuthCredentials throughout the network stack instead of username/password.

net/url_request/url_request_test_util.cc

Index: net/url_request/url_request_test_util.cc
diff --git a/net/url_request/url_request_test_util.cc b/net/url_request/url_request_test_util.cc
index 768e5209b25705a5cf38783bae4b6389df344dd6..3a7533200a2aa7cf94782f0091fd45e88b85ab6a 100644
--- a/net/url_request/url_request_test_util.cc
+++ b/net/url_request/url_request_test_util.cc
@@ -195,8 +195,8 @@ void TestDelegate::OnReceivedRedirect(net::URLRequest* request,
 void TestDelegate::OnAuthRequired(net::URLRequest* request,
                                   net::AuthChallengeInfo* auth_info) {
   auth_required_ = true;
-  if (!username_.empty() || !password_.empty()) {
-    request->SetAuth(username_, password_);
+  if (!credentials_.Empty()) {
+    request->SetAuth(credentials_);
   } else {
     request->CancelAuth();
   }