Don't try to use explicit credentials with schemes that don't support it.

net/http/http_auth_controller.h

 // Copyright (c) 2011 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_CONTROLLER_H_
 #define NET_HTTP_HTTP_AUTH_CONTROLLER_H_
 #pragma once
 
 #include <set>
 #include <string>
@@ skipping 60 matching lines @@
 
   virtual scoped_refptr<AuthChallengeInfo> auth_info();
 
   virtual bool IsAuthSchemeDisabled(HttpAuth::Scheme scheme) const;
   virtual void DisableAuthScheme(HttpAuth::Scheme scheme);
 
  private:
   // Actions for InvalidateCurrentHandler()
   enum InvalidateHandlerAction {
     INVALIDATE_HANDLER_AND_CACHED_CREDENTIALS,
+    INVALIDATE_HANDLER_AND_DISABLE_SCHEME,
     INVALIDATE_HANDLER
   };
 
   // So that we can mock this object.
   friend class base::RefCounted<HttpAuthController>;
 
   virtual ~HttpAuthController();
 
   // Searches the auth cache for an entry that encompasses the request's path.
   // If such an entry is found, updates |identity_| and |handler_| with the
@@ skipping 72 matching lines @@
 
   std::set<HttpAuth::Scheme> disabled_schemes_;
 
   CompletionCallbackImpl<HttpAuthController> io_callback_;
   CompletionCallback* user_callback_;
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_AUTH_CONTROLLER_H_