Add RELATIVE_ORIENTATION sensor implementation on macOS to //device/generic_sensor

device/generic_sensor/public/cpp/sensor_reading.h

Index: device/generic_sensor/public/cpp/sensor_reading.h
diff --git a/device/generic_sensor/public/cpp/sensor_reading.h b/device/generic_sensor/public/cpp/sensor_reading.h
index a7048f7a9a348a8b59e7f901d90ee2b0c8db7cbf..871e67d5d8a957a5f9d70ae059454daccdc48b0c 100644
--- a/device/generic_sensor/public/cpp/sensor_reading.h
+++ b/device/generic_sensor/public/cpp/sensor_reading.h
@@ -111,6 +111,10 @@ struct DEVICE_GENERIC_SENSOR_PUBLIC_EXPORT SensorReadingSharedBuffer {
   static uint64_t GetOffset(mojom::SensorType type);
 };
 
+bool DEVICE_GENERIC_SENSOR_PUBLIC_EXPORT
+GetSensorReadingFromBuffer(const SensorReadingSharedBuffer* buffer,
+                           SensorReading* result);
+
 }  // namespace device
 
 #endif  // DEVICE_GENERIC_SENSOR_PUBLIC_CPP_SENSOR_READING_H_