[sensors](CrOS/Linux) Implement Sensor device manager for sensors

device/generic_sensor/platform_sensor_provider_base.h

Index: device/generic_sensor/platform_sensor_provider_base.h
diff --git a/device/generic_sensor/platform_sensor_provider_base.h b/device/generic_sensor/platform_sensor_provider_base.h
index b6c33b1e29b71daa56109fbee0d08119455f37a1..6a5856467e43b80911b0bc02e3eaaf98a4b0ed73 100644
--- a/device/generic_sensor/platform_sensor_provider_base.h
+++ b/device/generic_sensor/platform_sensor_provider_base.h
@@ -53,6 +53,10 @@ class DEVICE_GENERIC_SENSOR_EXPORT PlatformSensorProviderBase
   // are no sensors left.
   virtual void AllSensorsRemoved() {}
 
+  // Implementations might override this method to know what type of sensor
+  // has been removed.
+  virtual void SensorRemoved(mojom::SensorType type) {}
+
  private:
   friend class PlatformSensor;  // To call RemoveSensor();