[net/http auth] Cleanup. Method names, and constness.

net/http/http_auth_multi_round_parse.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_HTTP_HTTP_AUTH_MULTI_ROUND_PARSE_H_
 #define NET_HTTP_HTTP_AUTH_MULTI_ROUND_PARSE_H_
 
 #include <string>
 
 #include "net/base/net_export.h"
 #include "net/http/http_auth.h"
 
 namespace net {
 
 class HttpAuthChallengeTokenizer;
 
 NET_EXPORT_PRIVATE HttpAuth::AuthorizationResult ParseFirstRoundChallenge(
     const std::string& scheme,
-    HttpAuthChallengeTokenizer* challenge);
+    const HttpAuthChallengeTokenizer& challenge);
 
 NET_EXPORT_PRIVATE HttpAuth::AuthorizationResult ParseLaterRoundChallenge(
     const std::string& scheme,
-    HttpAuthChallengeTokenizer* challenge,
+    const HttpAuthChallengeTokenizer& challenge,
     std::string* encoded_token,
     std::string* decoded_token);
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_AUTH_MULTI_ROUND_PARSE_H_