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

net/http/http_auth_handler_mock.h

Index: net/http/http_auth_handler_mock.h
diff --git a/net/http/http_auth_handler_mock.h b/net/http/http_auth_handler_mock.h
index e7d59972c1e31a7e751e920834898d7b5924ada9..14062397e9804386eaa78d95664c9efd9cf764a3 100644
--- a/net/http/http_auth_handler_mock.h
+++ b/net/http/http_auth_handler_mock.h
@@ -75,14 +75,24 @@ class HttpAuthHandlerMock : public HttpAuthHandler {
     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);
@@ -106,6 +116,8 @@ class HttpAuthHandlerMock : public HttpAuthHandler {
   std::string* auth_token_;
   bool first_round_;
   bool connection_based_;
+  bool allows_default_credentials_;
+  bool allows_explicit_credentials_;
   GURL request_url_;
 };