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

device/generic_sensor/platform_sensor_util_mac.h

Index: device/generic_sensor/platform_sensor_util_mac.h
diff --git a/device/generic_sensor/platform_sensor_util_mac.h b/device/generic_sensor/platform_sensor_util_mac.h
new file mode 100644
index 0000000000000000000000000000000000000000..c875bf1ca932407bd121f1c69569eb38aa85f277
--- /dev/null
+++ b/device/generic_sensor/platform_sensor_util_mac.h
@@ -0,0 +1,16 @@
+// 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_GENERIC_SENSOR_PLATFORM_SENSOR_UTIL_MAC_H_
+#define DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_UTIL_MAC_H_
+
+#include <stdint.h>
+
+namespace device {
+
+double LMUvalueToLux(uint64_t raw_value);
+
+}  // namespace device
+
+#endif  // DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_UTIL_MAC_H_