Currently Gecko uses SENSOR_ORIENTATION to calculate orientation. But SENSOR_ORIENTATION has become obsolete in android (http://developer.android.com/reference/android/hardware/Sensor.html) and android is not using that anymore. Android Jellybean has better orientation logic which is derived using SENSOR_TYPE_ACCELEROMETER HAL events. So we want to port android orientation calculation logic in gecko and we also want gecko to use SENSOR_TYPE_ACCELEROMETER for this calculation.

Please also note that SENSOR_TYPE_ORIENTATION is known to use more power. So it is not good to use it for orientation.