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

content/browser/device_sensors/data_fetcher_shared_memory_mac.cc

Index: content/browser/device_sensors/data_fetcher_shared_memory_mac.cc
diff --git a/content/browser/device_sensors/data_fetcher_shared_memory_mac.cc b/content/browser/device_sensors/data_fetcher_shared_memory_mac.cc
index 15bde3362a095dd3908c182220d6f2775287ea65..ab455aa6949b9185c7134899a173a8272b2f04ad 100644
--- a/content/browser/device_sensors/data_fetcher_shared_memory_mac.cc
+++ b/content/browser/device_sensors/data_fetcher_shared_memory_mac.cc
@@ -10,33 +10,13 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "content/browser/device_sensors/ambient_light_mac.h"
+#include "device/sensors/public/cpp/device_util_mac.h"
 #include "third_party/sudden_motion_sensor/sudden_motion_sensor_mac.h"
 
 namespace {
 
 const double kMeanGravity = 9.80665;
 
-double LMUvalueToLux(uint64_t raw_value) {
-  // Conversion formula from regression.
-  // https://bugzilla.mozilla.org/show_bug.cgi?id=793728
-  // Let x = raw_value, then
-  // lux = -2.978303814*(10^-27)*x^4 + 2.635687683*(10^-19)*x^3 -
-  //       3.459747434*(10^-12)*x^2 + 3.905829689*(10^-5)*x - 0.1932594532
-
-  static const long double k4 = pow(10.L, -7);
-  static const long double k3 = pow(10.L, -4);
-  static const long double k2 = pow(10.L, -2);
-  static const long double k1 = pow(10.L, 5);
-  long double scaled_value = raw_value / k1;
-
-  long double lux_value =
-      (-3 * k4 * pow(scaled_value, 4)) + (2.6 * k3 * pow(scaled_value, 3)) +
-      (-3.4 * k2 * pow(scaled_value, 2)) + (3.9 * scaled_value) - 0.19;
-
-  double lux = ceil(static_cast<double>(lux_value));
-  return lux > 0 ? lux : 0;
-}
-
 void FetchLight(content::AmbientLightSensor* sensor,
                 content::DeviceLightHardwareBuffer* buffer) {
   DCHECK(sensor);
@@ -48,7 +28,7 @@ void FetchLight(content::AmbientLightSensor* sensor,
   if (!sensor->ReadSensorValue(lux_value))
     return;
   uint64_t mean = (lux_value[0] + lux_value[1]) / 2;
-  double lux = LMUvalueToLux(mean);
+  double lux = device::LMUvalueToLux(mean);
   buffer->seqlock.WriteBegin();
   buffer->data.value = lux;
   buffer->seqlock.WriteEnd();