Extract IsKnownRoot() functionality for testing if a certificate is a

net/cert/known_roots_nss.cc

+// Copyright (c) 2017 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/cert/known_roots_nss.h"
+
+#include <cert.h>
+#include <pk11pub.h>
+
+#include <memory>
+
+namespace net {
+
+// IsKnownRoot returns true if the given certificate is one that we believe
+// is a standard (as opposed to user-installed) root.
+bool IsKnownRoot(CERTCertificate* root) {
+  if (!root || !root->slot)
+    return false;
+
+  // This magic name is taken from
+  // http://bonsai.mozilla.org/cvsblame.cgi?file=mozilla/security/nss/lib/ckfw/builtins/constants.c&rev=1.13&mark=86,89#79
+  return 0 == strcmp(PK11_GetSlotName(root->slot), "NSS Builtin Objects");
+}
+
+}  // namespace net