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

net/ftp/ftp_transaction.h

Index: net/ftp/ftp_transaction.h
diff --git a/net/ftp/ftp_transaction.h b/net/ftp/ftp_transaction.h
index 300468ba2fe8a43f3b673513cc8c5050b30a11ba..cc2f46ef90af9c77eb20860ba5d6df1d2ef7ee24 100644
--- a/net/ftp/ftp_transaction.h
+++ b/net/ftp/ftp_transaction.h
@@ -14,6 +14,7 @@
 
 namespace net {
 
+class AuthCredentials;
 class FtpResponseInfo;
 class FtpRequestInfo;
 class BoundNetLog;
@@ -44,8 +45,7 @@ class NET_EXPORT_PRIVATE FtpTransaction {
                     const BoundNetLog& net_log) = 0;
 
   // Restarts the FTP transaction with authentication credentials.
-  virtual int RestartWithAuth(const string16& username,
-                              const string16& password,
+  virtual int RestartWithAuth(const AuthCredentials& credentials,
                               OldCompletionCallback* callback) = 0;
 
   // Once response info is available for the transaction, response data may be