[net/http auth] Use strings to identify authentication schemes.

net/http/http_auth_challenge_tokenizer.h

 // Copyright 2014 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_CHALLENGE_TOKENIZER_
 #define NET_HTTP_HTTP_AUTH_CHALLENGE_TOKENIZER_
 
 #include <string>
 
 #include "net/base/net_export.h"
@@ skipping 13 matching lines @@
  public:
   HttpAuthChallengeTokenizer(std::string::const_iterator begin,
                              std::string::const_iterator end);
   ~HttpAuthChallengeTokenizer();
 
   // Get the original text.
   std::string challenge_text() const {
     return std::string(begin_, end_);
   }
 
-  // Get the auth scheme of the challenge.
+  // Get the auth scheme of the challenge. Could potentially be invalid.
   std::string::const_iterator scheme_begin() const { return scheme_begin_; }
   std::string::const_iterator scheme_end() const { return scheme_end_; }
-  std::string scheme() const {
-    return std::string(scheme_begin_, scheme_end_);
-  }
+
+  // Return the normalized scheme for the challenge. Will be empty if the
+  // challenge was invalid. RFC 7235 requires a valid scheme to be a token. A
+  // normalized scheme is a lower case ASCII token.
+  std::string NormalizedScheme() const;
+
+  // Returns true if the scheme of the challenge is |scheme|. |scheme| is
+  // expected to be a valid scheme.
+  bool SchemeIs(const base::StringPiece& scheme) const;
 
   std::string::const_iterator params_begin() const { return params_begin_; }
   std::string::const_iterator params_end() const { return params_end_; }
   HttpUtil::NameValuePairsIterator param_pairs() const;
   std::string base64_param() const;
 
  private:
   void Init(std::string::const_iterator begin,
             std::string::const_iterator end);
 
   std::string::const_iterator begin_;
   std::string::const_iterator end_;
 
   std::string::const_iterator scheme_begin_;
   std::string::const_iterator scheme_end_;
 
   std::string::const_iterator params_begin_;
   std::string::const_iterator params_end_;
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_AUTH_CHALLENGE_TOKENIZER_