Use SSPI for NTLM authentication on Windows....

net/http/http_auth_handler.h

Index: net/http/http_auth_handler.h
===================================================================
--- net/http/http_auth_handler.h	(revision 24540)
+++ net/http/http_auth_handler.h	(working copy)
@@ -68,6 +68,11 @@
   // sequence used by a connection-based authentication scheme.
   virtual bool NeedsIdentity() { return true; }
 
+  // Returns true if this is the final round of the authentication sequence.
+  // For Basic and Digest, the method always returns true because they are
+  // single-round schemes.
+  virtual bool IsFinalRound() { return true; }
+
   // Generate the Authorization header value.
   virtual std::string GenerateCredentials(const std::wstring& username,
                                           const std::wstring& password,