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

net/http/http_auth_controller.h

Index: net/http/http_auth_controller.h
===================================================================
--- net/http/http_auth_controller.h	(revision 120359)
+++ net/http/http_auth_controller.h	(working copy)
@@ -33,6 +33,14 @@
     : public base::RefCounted<HttpAuthController>,
       NON_EXPORTED_BASE(public base::NonThreadSafe) {
  public:
+  // Options for the handling of auth challenges.
+  enum ChallengeOption {
+    CHALLENGE_OPTION_NONE = 0,
+    CHALLENGE_OPTION_SEND_SERVER_AUTH = 1,

[cbentzel, 2012/02/06 15:55:38]

Perhaps 0x1 << 0, 0x1 << 2, etc. to better indicate that this a bitmask.

[Tom Sepez, 2012/02/06 18:05:30]

Sure, will do.

+    CHALLENGE_OPTION_USE_EMBEDDED_AUTH = 2,
+    CHALLENGE_OPTION_ESTABLISHING_TUNNEL = 4

[cbentzel, 2012/02/06 15:55:38]

"ESTABLISHING_TUNNEL" doesn't feel like much of an option - it's more of a
description of the current state. If you want to lump it in here to make callers
more obvious, I guess I'm OK but it feels like a stretch.

[Tom Sepez, 2012/02/06 18:05:30]

Understood.  I'd like to keep it here though for the sake of clarity.

+  };
+
   // The arguments are self explanatory except possibly for |auth_url|, which
   // should be both the auth target and auth path in a single url argument.
   HttpAuthController(HttpAuth::Target target,
@@ -57,8 +65,7 @@
   // |HandleAuthChallenge()| returns OK on success, or a network error code
   // otherwise. It may also populate |auth_info_|.
   virtual int HandleAuthChallenge(scoped_refptr<HttpResponseHeaders> headers,
-                                  bool do_not_send_server_auth,
-                                  bool establishing_tunnel,
+                                  int challenge_option_mask,

[cbentzel, 2012/02/06 15:55:38]

ChallengeOption should be fine here.

[Tom Sepez, 2012/02/06 18:05:30]

It's that idiotic way that c++ handles or's of enums, which result in type int
and can't be passed to the enum without a cast by the caller, which is nice to
avoid.  I'll change it,

                                   const BoundNetLog& net_log);
 
   // Store the supplied credentials and prepare to restart the auth.
@@ -103,7 +110,7 @@
   // Sets |identity_| to the next identity that the transaction should try. It
   // chooses candidates by searching the auth cache and the URL for a
   // username:password. Returns true if an identity was found.
-  bool SelectNextAuthIdentityToTry();
+  bool SelectNextAuthIdentityToTry(int challenge_option_mask);
 
   // Populates auth_info_ with the challenge information, so that
   // URLRequestHttpJob can prompt for credentials.