[sensors] [mac] Implement ambient light sensor for macOS

device/base/device_util_mac.h

+// Copyright 2016 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 DEVICE_BASE_DEVICE_UTIL_MAC_H_
+#define DEVICE_BASE_DEVICE_UTIL_MAC_H_
+
+#include <stdint.h>
+
+namespace device {
+
+// Convert the value returned by the ambient light LMU sensor on Mac
+// hardware to a lux value.
+double LMUvalueToLux(uint64_t raw_value);

[Reilly Grant (use Gerrit), 2016/10/04 07:11:27]

This seems to be specific to light sensors. Any reason it isn't in
//device/generic_sensor?

+
+}  // namespace device
+
+#endif  // DEVICE_BASE_DEVICE_UTIL_MAC_H_