Initial implementation of music manager private API.

chrome/browser/extensions/api/music_manager_private/device_id.h

Index: chrome/browser/extensions/api/music_manager_private/device_id.h
diff --git a/chrome/browser/extensions/api/music_manager_private/device_id.h b/chrome/browser/extensions/api/music_manager_private/device_id.h
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+++ b/chrome/browser/extensions/api/music_manager_private/device_id.h
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+// Copyright 2013 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_EXTENSIONS_API_MUSIC_MANAGER_PRIVATE_DEVICE_ID_H_
+#define CHROME_BROWSER_EXTENSIONS_API_MUSIC_MANAGER_PRIVATE_DEVICE_ID_H_
+
+#include <string>
+
+namespace device_id {
+
+// Return a "device" identifier with the following characteristics:
+// 1. The id is shared across users of a device.
+// 2. The id is resilient to device reboots.
+// 3. There is *some* way for the identifier to be reset (e.g. it can *not* be
+//    the MAC address of the device's network card).
+// The specific implementation varies across platforms, but is currently
+// fast enough that it can be run on the UI thread.
+// The returned value is HMAC_SHA256(device_id, |salt|), so that the actual
+// device identifier value is not exposed directly to the caller.
+std::string GetDeviceID(const std::string& salt);
+
+}  // namespace device_id
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_MUSIC_MANAGER_PRIVATE_DEVICE_ID_H_