[Device Service] Add RELATIVE_ORIENTATION sensor type 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 81e2f76822c58886b72e409563e94086bd74f252..a7048f7a9a348a8b59e7f901d90ee2b0c8db7cbf 100644
--- a/device/generic_sensor/public/cpp/sensor_reading.h
+++ b/device/generic_sensor/public/cpp/sensor_reading.h
@@ -46,6 +46,56 @@ struct DEVICE_GENERIC_SENSOR_PUBLIC_EXPORT SensorReading {
   SensorReading(const SensorReading& other);
   SensorReadingField<double> timestamp;
   constexpr static int kValuesCount = 4;
+  // AMBIENT_LIGHT:
+  // values[0]: ambient light level in SI lux units.
+  //
+  // PROXIMITY:
+  // values[0]: proximity sensor distance measured in centimeters.
+  //
+  // ACCELEROMETER:
+  // values[0]: acceleration minus Gx on the x-axis.
+  // values[1]: acceleration minus Gy on the y-axis.
+  // values[2]: acceleration minus Gz on the z-axis.
+  //
+  // LINEAR_ACCELERATION:
+  // values[0]: acceleration on the x-axis.
+  // values[1]: acceleration on the y-axis.
+  // values[2]: acceleration on the z-axis.
+  //
+  // GYROSCOPE:
+  // values[0]: angular speed around the x-axis.
+  // values[1]: angular speed around the y-axis.
+  // values[2]: angular speed around the z-axis.
+  //
+  // MAGNETOMETER:
+  // values[0]: ambient magnetic field in the x-axis in micro-Tesla (uT).
+  // values[1]: ambient magnetic field in the y-axis in micro-Tesla (uT).
+  // values[2]: ambient magnetic field in the z-axis in micro-Tesla (uT).
+  //
+  // PRESSURE:
+  // values[0]: atmospheric pressure in hPa (millibar).
+  //
+  // ABSOLUTE_ORIENTATION:
+  // values[0]: x value of a quaternion representing the orientation of the
+  // device in 3D space.
+  // values[1]: y value of a quaternion representing the orientation of the
+  // device in 3D space.
+  // values[2]: z value of a quaternion representing the orientation of the
+  // device in 3D space.
+  // values[3]: w value of a quaternion representing the orientation of the
+  // device in 3D space.
+  //
+  // RELATIVE_ORIENTATION:
+  // (Identical to ABSOLUTE_ORIENTATION except that it doesn't use the
+  // geomagnetic field.)
+  // values[0]: x value of a quaternion representing the orientation of the
+  // device in 3D space.
+  // values[1]: y value of a quaternion representing the orientation of the
+  // device in 3D space.
+  // values[2]: z value of a quaternion representing the orientation of the
+  // device in 3D space.
+  // values[3]: w value of a quaternion representing the orientation of the
+  // device in 3D space.

[dcheng, 2017/05/03 20:58:53]

Maybe we should be using a union? That seems like it'd much more self
documenting and less prone to randomly using the wrong index. Something else to
consider as a followup...

[juncai, 2017/05/04 17:51:09]

Filed bug:
https://bugs.chromium.org/p/chromium/issues/detail?id=718459
I will consider fixing it in a follow-up CL.

   SensorReadingField<double> values[kValuesCount];
 };