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

net/url_request/url_request_unittest.cc

Index: net/url_request/url_request_unittest.cc
===================================================================
--- net/url_request/url_request_unittest.cc	(revision 120359)
+++ net/url_request/url_request_unittest.cc	(working copy)
@@ -2454,6 +2454,7 @@
     d.set_credentials(AuthCredentials(kUser, kSecret));
 
     URLRequest r(url_requiring_auth, &d);
+    r.set_load_flags(LOAD_NORMAL | LOAD_ENABLE_EMBEDDED_IDENTITY);
     r.set_context(context);
     r.Start();
 
@@ -2485,6 +2486,7 @@
     GURL url_with_identity = url_requiring_auth.ReplaceComponents(replacements);
 
     URLRequest r(url_with_identity, &d);
+    r.set_load_flags(LOAD_NORMAL | LOAD_ENABLE_EMBEDDED_IDENTITY);
     r.set_context(context);
     r.Start();