widevine: Support CDM host verification and storage ID (fixes issue #3404)

This functionality will be enabled if .sig files exist in the required
locations. See the issue for details.

libcef/common/cdm_host_file_path.h

@@ -0,0 +1,20 @@
+// Copyright 2022 The Chromium Embedded Framework Authors. Portions Copyright
+// 2017 The Chromium Authors. Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#ifndef CEF_LIBCEF_COMMON_CDM_HOST_FILE_PATH_H_
+#define CEF_LIBCEF_COMMON_CDM_HOST_FILE_PATH_H_
+
+#include <vector>
+
+#include "media/cdm/cdm_host_file.h"
+
+namespace cef {
+
+// Gets a list of CDM host file paths and put them in |cdm_host_file_paths|.
+void AddCdmHostFilePaths(
+    std::vector<media::CdmHostFilePath>* cdm_host_file_paths);
+
+}  // namespace cef
+
+#endif  // CEF_LIBCEF_COMMON_CDM_HOST_FILE_PATH_H_