[Device Service] Add RELATIVE_ORIENTATION sensor type to //device/generic_sensor

device/generic_sensor/public/interfaces/sensor.mojom

 // Copyright 2016 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.
 
 module device.mojom;
 
 // Types of supported sensors
+// When adding new sensor type, update the documentation of sensor data values
+// in SensorReading struct at sensor_reading.h file.
 enum SensorType {
   FIRST = 1,
   AMBIENT_LIGHT = FIRST,
   PROXIMITY,
   ACCELEROMETER,
   LINEAR_ACCELERATION,
   GYROSCOPE,
   MAGNETOMETER,
   PRESSURE,
   ABSOLUTE_ORIENTATION,
-  LAST = ABSOLUTE_ORIENTATION // Note: LAST is also equal to the types count.
+  RELATIVE_ORIENTATION,
+  LAST = RELATIVE_ORIENTATION // Note: LAST is also equal to the types count.
 };
 
 // Reporting mode supported by the Sensor.
 // ON_CHANGE  - client will be notified through OnSensorReadingChanged() signal
 //              whenever sensor reading is changed.
 // CONTINUOUS - sensor will continuously update its reading with frequency
 //              specified in SensorConfiguration.frequency.
 //              OnSensorReadingChanged() signal is not sent to the client for
 //              sensors with CONTINUOUS reporting mode.
 enum ReportingMode {
@@ skipping 50 matching lines @@
 // Interface that client of the Sensor interface must implement to observe
 // sensor reading changes and error conditions.
 interface SensorClient {
   // Signals SensorClient when there is an error.
   RaiseError();
 
   // Signals SensorClient when reading has been changed (only for sensors with
   // ReportingMode::ON_CHANGE).
   SensorReadingChanged();
 };