Integration tests for WebStateDelegate::OnAuthRequired callback.

ios/web/public/test/fakes/test_web_state_delegate.h

Index: ios/web/public/test/fakes/test_web_state_delegate.h
diff --git a/ios/web/public/test/fakes/test_web_state_delegate.h b/ios/web/public/test/fakes/test_web_state_delegate.h
index e1eb13e32bc2d96b283b7bd04e23f203f495cf5f..2cdd680f3228119925da739decde0512bdf21eee 100644
--- a/ios/web/public/test/fakes/test_web_state_delegate.h
+++ b/ios/web/public/test/fakes/test_web_state_delegate.h
@@ -65,6 +65,11 @@ class TestWebStateDelegate : public WebStateDelegate {
     return last_authentication_request_.get();
   }
 
+  // Clears the last HTTP Authentication request passed to |OnAuthRequired|.
+  void ClearLastAuthenticationRequest() {
+    last_authentication_request_.reset();
+  }
+
  private:
   bool load_progress_changed_called_ = false;
   bool handle_context_menu_called_ = false;