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

net/url_request/url_request_job.cc

Index: net/url_request/url_request_job.cc
diff --git a/net/url_request/url_request_job.cc b/net/url_request/url_request_job.cc
index 8390d8c2f7ee9a74fd304e9644581b2c5ba1823a..a9e96272ede9650b73341a50369ba42534a16309 100644
--- a/net/url_request/url_request_job.cc
+++ b/net/url_request/url_request_job.cc
@@ -153,8 +153,7 @@ void URLRequestJob::GetAuthChallengeInfo(
   NOTREACHED();
 }
 
-void URLRequestJob::SetAuth(const string16& username,
-                            const string16& password) {
+void URLRequestJob::SetAuth(const AuthCredentials& credentials) {
   // This will only be called if NeedsAuth() returns true, in which
   // case the derived class should implement this!
   NOTREACHED();