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

net/http/http_auth_sspi_win.h

Index: net/http/http_auth_sspi_win.h
diff --git a/net/http/http_auth_sspi_win.h b/net/http/http_auth_sspi_win.h
index b3ef3c9581ff23057492ae52d4eded9531b4b13c..cfb4cc03d8a2d26be534f2204b4774403aa34c00 100644
--- a/net/http/http_auth_sspi_win.h
+++ b/net/http/http_auth_sspi_win.h
@@ -145,8 +145,7 @@ class NET_EXPORT_PRIVATE HttpAuthSSPI {
   // obtained using |*username| and |*password|. If |username| and |password|
   // are both NULL, the credentials for the currently logged in user are used
   // instead.
-  int GenerateAuthToken(const string16* username,
-                        const string16* password,
+  int GenerateAuthToken(const AuthCredentials* credentials,
                         const std::wstring& spn,
                         std::string* auth_token);
 
@@ -156,7 +155,7 @@ class NET_EXPORT_PRIVATE HttpAuthSSPI {
   void Delegate();
 
  private:
-  int OnFirstRound(const string16* username, const string16* password);
+  int OnFirstRound(const AuthCredentials* credentials);
 
   int GetNextSecurityToken(
       const std::wstring& spn,