[sensors][mac] Make sure to update the sensor value when initializing the sensor.

device/generic_sensor/platform_sensor_ambient_light_mac.cc

Index: device/generic_sensor/platform_sensor_ambient_light_mac.cc
diff --git a/device/generic_sensor/platform_sensor_ambient_light_mac.cc b/device/generic_sensor/platform_sensor_ambient_light_mac.cc
index 7256cfb4bb72491b2f84823a0a38f1399fdfc6bf..b6f162b89d4e262e2cce5931a4096b49d1a94515 100644
--- a/device/generic_sensor/platform_sensor_ambient_light_mac.cc
+++ b/device/generic_sensor/platform_sensor_ambient_light_mac.cc
@@ -54,14 +54,7 @@ void PlatformSensorAmbientLightMac::IOServiceCallback(void* context,
                                                       void* message_argument) {
   PlatformSensorAmbientLightMac* sensor =
       static_cast<PlatformSensorAmbientLightMac*>(context);
-  uint32_t scalar_output_count = 2;
-  uint64_t lux_values[2];
-  kern_return_t kr = IOConnectCallMethod(
-      sensor->light_sensor_object_, LmuFunctionIndex::kGetSensorReadingID,
-      nullptr, 0, nullptr, 0, lux_values, &scalar_output_count, nullptr, 0);
-
-  if (kr == KERN_SUCCESS)
-    sensor->UpdateReading(lux_values);
+  sensor->ReadSensorValue();

[timvolodine, 2016/10/18 19:26:13]

would it make sense to make ReadSensorValue return void and return true in
StartSensor below?

[darktears, 2016/10/18 19:56:58]

The idea here was that at some point we will need to report the error back in
JavaScript. So here I would get the return value and do what's needed to throw
it in JavaScript.

 }
 
 bool PlatformSensorAmbientLightMac::StartSensor(
@@ -100,8 +93,10 @@ bool PlatformSensorAmbientLightMac::StartSensor(
 
   kr = IOServiceOpen(light_sensor_service_, mach_task_self(), 0,
                      light_sensor_object_.InitializeInto());
+  if (kr != KERN_SUCCESS)
+    return false;
 
-  return kr == KERN_SUCCESS;
+  return ReadSensorValue();

[timvolodine, 2016/10/18 19:26:13]

is it possible that ReadSensorValue returns false but later the callback is
still executed. Also, in that case do you need to unregister the callback?

[darktears, 2016/10/18 19:56:58]

Yes then we can clean it up.

 }
 
 void PlatformSensorAmbientLightMac::StopSensor() {
@@ -111,17 +106,27 @@ void PlatformSensorAmbientLightMac::StopSensor() {
   current_lux_ = 0.0;
 }
 
-void PlatformSensorAmbientLightMac::UpdateReading(uint64_t lux_values[2]) {
+bool PlatformSensorAmbientLightMac::ReadSensorValue() {

[timvolodine, 2016/10/18 19:26:13]

maybe better name something like: ReadAndUpdate.. or ReadAndNotify?

[darktears, 2016/10/18 19:56:58]

I will change.

+  uint32_t scalar_output_count = 2;
+  uint64_t lux_values[2];
+  kern_return_t kr = IOConnectCallMethod(
+      light_sensor_object_, LmuFunctionIndex::kGetSensorReadingID, nullptr, 0,
+      nullptr, 0, lux_values, &scalar_output_count, nullptr, 0);
+
+  if (kr != KERN_SUCCESS)
+    return false;
+
   uint64_t mean = (lux_values[0] + lux_values[1]) / 2;
   double lux = LMUvalueToLux(mean);
   if (lux == current_lux_)
-    return;
+    return true;
   current_lux_ = lux;
 
   SensorReading reading;
   reading.timestamp = (base::TimeTicks::Now() - base::TimeTicks()).InSecondsF();
   reading.values[0] = current_lux_;
   UpdateSensorReading(reading, true);
+  return true;
 }
 
 }  // namespace device