Don't use IDENT_SRC_URL for HttpAuth challenges. IE hasn't supported it for years, and at worst ...

net/http/http_network_transaction.cc

 // Copyright (c) 2012 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.
 
 #include "net/http/http_network_transaction.h"
 
 #include <set>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 1272 matching lines @@
   HttpAuth::Target target = status == 407 ?
                             HttpAuth::AUTH_PROXY : HttpAuth::AUTH_SERVER;
   if (target == HttpAuth::AUTH_PROXY && proxy_info_.is_direct())
     return ERR_UNEXPECTED_PROXY_AUTH;
 
   // This case can trigger when an HTTPS server responds with a 407 status
   // code through a non-authenticating proxy.
   if (!auth_controllers_[target].get())
     return ERR_UNEXPECTED_PROXY_AUTH;
 
+  int option_mask = 0;
+  if (!(request_->load_flags & LOAD_DO_NOT_SEND_AUTH_DATA))
+    option_mask |= HttpAuthController::CHALLENGE_OPTION_SEND_SERVER_AUTH;
+  if ((request_->load_flags & LOAD_ENABLE_EMBEDDED_IDENTITY))
+    option_mask |= HttpAuthController::CHALLENGE_OPTION_USE_EMBEDDED_AUTH;
+
   int rv = auth_controllers_[target]->HandleAuthChallenge(
-      headers, (request_->load_flags & LOAD_DO_NOT_SEND_AUTH_DATA) != 0, false,
-      net_log_);
+      headers, option_mask, net_log_);
   if (auth_controllers_[target]->HaveAuthHandler())
       pending_auth_target_ = target;
 
   scoped_refptr<AuthChallengeInfo> auth_info =
       auth_controllers_[target]->auth_info();
   if (auth_info.get())
       response_.auth_challenge = auth_info;
 
   return rv;
 }
@@ skipping 46 matching lines @@
       description = base::StringPrintf("Unknown state 0x%08X (%u)", state,
                                        state);
       break;
   }
   return description;
 }
 
 #undef STATE_CASE
 
 }  // namespace net