Implement the NTLM authentication scheme by porting...

net/http/http_auth.h

 // Copyright (c) 2006-2008 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_H_
 #define NET_HTTP_HTTP_AUTH_H_
 
 #include "base/ref_counted.h"
 #include "net/http/http_util.h"
 
@@ skipping 35 matching lines @@
      IDENT_SRC_EXTERNAL,
    };
 
    // Helper structure used by HttpNetworkTransaction to track 
    // the current identity being used for authorization.
    struct Identity {
      Identity() : source(IDENT_SRC_NONE), invalid(true) { }
 
      IdentitySource source;
      bool invalid;
+     // TODO(wtc): |username| and |password| should be string16.
      std::wstring username;
      std::wstring password;
    };
 
   // Get the name of the header containing the auth challenge
   // (either WWW-Authenticate or Proxy-Authenticate).
   static std::string GetChallengeHeaderName(Target target);
 
   // Get the name of the header where the credentials go
   // (either Authorization or Proxy-Authorization).
   static std::string GetAuthorizationHeaderName(Target target);
 
   // Create a handler to generate credentials for the challenge, and pass
   // it back in |*handler|. If the challenge is unsupported or invalid
   // |*handler| is set to NULL.
   static void CreateAuthHandler(const std::string& challenge,
                                 Target target,
                                 scoped_refptr<HttpAuthHandler>* handler);
 
   // Iterate through the challenge headers, and pick the best one that
   // we support. Obtains the implementation class for handling the challenge,
-  // and passes it back in |*handler|. If no supported challenge was found
-  // |*handler| is set to NULL.
+  // and passes it back in |*handler|. If the existing handler in |*handler|
+  // should continue to be used (such as for the NTLM authentication scheme),
+  // |*handler| is unchanged. If no supported challenge was found, |*handler|
+  // is set to NULL.
+  //
+  // TODO(wtc): Continuing to use the existing handler in |*handler| (for
+  // NTLM) is new behavior.  Rename ChooseBestChallenge to fully encompass
+  // what it does now.
   static void ChooseBestChallenge(const HttpResponseHeaders* headers,
                                   Target target,
                                   scoped_refptr<HttpAuthHandler>* handler);
 
   // ChallengeTokenizer breaks up a challenge string into the the auth scheme
   // and parameter list, according to RFC 2617 Sec 1.2:
   //    challenge = auth-scheme 1*SP 1#auth-param
   //
   // Check valid() after each iteration step in case it was malformed.
   // Also note that value() will give whatever is to the right of the equals
@@ skipping 58 matching lines @@
     std::string::const_iterator value_begin_;
     std::string::const_iterator value_end_;
 
     bool value_is_quoted_;
   };
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_AUTH_H_