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

net/http/http_auth_handler_mock.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_HANDLER_MOCK_H_
 #define NET_HTTP_HTTP_AUTH_HANDLER_MOCK_H_
 #pragma once
 
 #include <string>
 
@@ skipping 57 matching lines @@
   virtual int ResolveCanonicalName(HostResolver* host_resolver,
                                    CompletionCallback* callback);
 
 
   void SetGenerateExpectation(bool async, int rv);
 
   void set_connection_based(bool connection_based) {
     connection_based_ = connection_based;
   }
 
+  void set_allows_default_credentials(bool allows_default_credentials) {
+    allows_default_credentials_ = allows_default_credentials;
+  }
+
+  void set_allows_explicit_credentials(bool allows_explicit_credentials) {
+    allows_explicit_credentials_ = allows_explicit_credentials;
+  }
+
   const GURL& request_url() const {
     return request_url_;
   }
 
   // HttpAuthHandler:
   virtual HttpAuth::AuthorizationResult HandleAnotherChallenge(
-      HttpAuth::ChallengeTokenizer* challenge);
-  virtual bool NeedsIdentity();
+      HttpAuth::ChallengeTokenizer* challenge) OVERRIDE;
+  virtual bool NeedsIdentity() OVERRIDE;
+  virtual bool AllowsDefaultCredentials() OVERRIDE;
+  virtual bool AllowsExplicitCredentials() OVERRIDE;
 
  protected:
   virtual bool Init(HttpAuth::ChallengeTokenizer* challenge);
 
   virtual int GenerateAuthTokenImpl(const string16* username,
                                     const string16* password,
                                     const HttpRequestInfo* request,
                                     CompletionCallback* callback,
                                     std::string* auth_token);
 
  private:
   void OnResolveCanonicalName();
 
   void OnGenerateAuthToken();
 
   Resolve resolve_;
   CompletionCallback* user_callback_;
   ScopedRunnableMethodFactory<HttpAuthHandlerMock> method_factory_;
   bool generate_async_;
   int generate_rv_;
   std::string* auth_token_;
   bool first_round_;
   bool connection_based_;
+  bool allows_default_credentials_;
+  bool allows_explicit_credentials_;
   GURL request_url_;
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_AUTH_HANDLER_MOCK_H_