Have the authenticating_url_loader cache token per-origin.

services/authenticating_url_loader/authenticating_url_loader_factory_impl.h

Index: services/authenticating_url_loader/authenticating_url_loader_factory_impl.h
diff --git a/services/authenticating_url_loader/authenticating_url_loader_factory_impl.h b/services/authenticating_url_loader/authenticating_url_loader_factory_impl.h
index 03f9307907ceb9248405aebacd1234a107ec8d75..f120cd3a1f4fd7a8d44338d371f3a8408e97d7d3 100644
--- a/services/authenticating_url_loader/authenticating_url_loader_factory_impl.h
+++ b/services/authenticating_url_loader/authenticating_url_loader_factory_impl.h
@@ -13,6 +13,7 @@
 #include "mojo/services/authenticating_url_loader/public/interfaces/authenticating_url_loader_factory.mojom.h"
 #include "mojo/services/authentication/public/interfaces/authentication.mojom.h"
 #include "mojo/services/network/public/interfaces/network_service.mojom.h"
+#include "url/gurl.h"
 
 namespace mojo {
 
@@ -46,6 +47,7 @@ class AuthenticatingURLLoaderFactoryImpl
   authentication::AuthenticationServicePtr authentication_service_;
   NetworkServicePtr network_service_;
   std::vector<std::unique_ptr<AuthenticatingURLLoaderImpl>> url_loaders_;
+  std::map<GURL, std::string> cached_tokens_;
 };
 
 }  // namespace mojo