Add a new function for getting a deterministic machine ID

chrome/browser/prefs/tracked/device_id.h

+// Copyright 2015 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 CHROME_BROWSER_PREFS_TRACKED_DEVICE_ID_H_
+#define CHROME_BROWSER_PREFS_TRACKED_DEVICE_ID_H_
+
+#include <string>
+
+namespace tracked_prefs {
+
+enum class MachineIdStatus {
+  SUCCESS = 0,
+  FAILURE,  // Returned if attempt to obtain a machine-specific ID fails.
+  NOT_IMPLEMENTED  // Returned if the method for obtaining a
+                   // machine-specific ID is not implemented for
+                   // the system.
+};
+
+// Populates |machine_id| with a deterministic ID for this
+// machine. |machine_id| must not be NULL. Returns |FAILURE| if a

[grt (UTC plus 2), 2015/01/27 17:06:22]

NULL -> null or nullptr. I prefer the former, but the latter is acceptable.

[alito, 2015/01/27 20:56:55]

Done.

+// machine ID cannot be obtained or |NOT_IMPLEMENTED| on systems for
+// which this feature is not supported (in both cases |machine_id| is
+// left untouched).
+MachineIdStatus GetDeterministicMachineSpecificId(std::string* machine_id);

[grt (UTC plus 2), 2015/01/27 17:06:22]

Do consumers of this function need to differentiate FAILURE from
NOT_IMPLEMENTED?

[gab, 2015/01/27 18:27:41]

Yes, they will, this is why we added this.

i.e. settings hardening and its metrics should care IMO.

+
+}  // namespace tracked_prefs
+
+#endif  // CHROME_BROWSER_PREFS_TRACKED_DEVICE_ID_H_