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

net/cert/known_roots_win.h

+// 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.
+
+#ifndef NET_CERT_KNOWN_ROOTS_WIN_H_
+#define NET_CERT_KNOWN_ROOTS_WIN_H_
+
+#include "crypto/wincrypt_shim.h"
+
+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(PCCERT_CONTEXT cert);
+
+}  // namespace net
+
+#endif  // NET_CERT_KNOWN_ROOTS_WIN_H_