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

net/http/http_auth_gssapi_posix.h

Index: net/http/http_auth_gssapi_posix.h
diff --git a/net/http/http_auth_gssapi_posix.h b/net/http/http_auth_gssapi_posix.h
index 3367713ef85a147b9eee5f37e924836f02f7d1ed..9391cfb7985636c5ba5e8edf3d527f5c52cb2d70 100644
--- a/net/http/http_auth_gssapi_posix.h
+++ b/net/http/http_auth_gssapi_posix.h
@@ -247,8 +247,7 @@ class NET_EXPORT_PRIVATE HttpAuthGSSAPI {
   // If this is the first round of a multiple round scheme, credentials are
   // obtained using |*username| and |*password|. If |username| and |password|
   // are NULL, the default credentials are used instead.
-  int GenerateAuthToken(const string16* username,
-                        const string16* password,
+  int GenerateAuthToken(const AuthCredentials* credentials,
                         const std::wstring& spn,
                         std::string* auth_token);