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

content/browser/device_sensors/data_fetcher_shared_memory_mac.cc

 // Copyright 2014 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.
 
 #include "content/browser/device_sensors/data_fetcher_shared_memory.h"
 
 #include <stdint.h>
 
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "content/browser/device_sensors/ambient_light_mac.h"
+#include "device/base/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);
   DCHECK(buffer);
   // Macbook pro has 2 lux values, left and right, we take the average.
   // The raw sensor values are converted to lux using LMUvalueToLux(raw_value)
   // similar to how it is done in Firefox.
   uint64_t lux_value[2];
   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();
 }
 
 void FetchMotion(SuddenMotionSensor* sensor,
     content::DeviceMotionHardwareBuffer* buffer) {
   DCHECK(sensor);
   DCHECK(buffer);
 
@@ skipping 209 matching lines @@
         light_buffer_ = nullptr;
       }
       return true;
     default:
       NOTREACHED();
   }
   return false;
 }
 
 }  // namespace content