Add a new function for getting a deterministic machine ID

chrome/browser/prefs/tracked/device_id.h

Index: chrome/browser/prefs/tracked/device_id.h
diff --git a/chrome/browser/prefs/tracked/device_id.h b/chrome/browser/prefs/tracked/device_id.h
new file mode 100644
index 0000000000000000000000000000000000000000..859e877901e0c92e3427ac0434889d8e2a3a248d
--- /dev/null
+++ b/chrome/browser/prefs/tracked/device_id.h
@@ -0,0 +1,29 @@
+// 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 MachineIdStatus {

[gab, 2015/01/26 19:40:46]

Use enum class (avoids polluting the namespace and is more explicit).

[alito, 2015/01/26 21:01:10]

Done.

+  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 be non-NULL and point to a valid
+// std::string object. Returns |FAILURE| if a machine ID cannot be

[gab, 2015/01/26 19:40:46]

Remove "and point to a a valid std::string object" (it's implied by the type
that callers shouldn't be stupid and cast some other pointer in there :-)!)

[alito, 2015/01/26 21:01:10]

Done.

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