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

device/generic_sensor/platform_sensor.h

Index: device/generic_sensor/platform_sensor.h
diff --git a/device/generic_sensor/platform_sensor.h b/device/generic_sensor/platform_sensor.h
index 94629a552b9d9abe55556bce46e78145afa448c5..c6878f75c41889c1a364f2d289b812179ba6ae92 100644
--- a/device/generic_sensor/platform_sensor.h
+++ b/device/generic_sensor/platform_sensor.h
@@ -41,6 +41,9 @@ class DEVICE_GENERIC_SENSOR_EXPORT PlatformSensor
 
   virtual mojom::ReportingMode GetReportingMode() = 0;
   virtual PlatformSensorConfiguration GetDefaultConfiguration() = 0;
+  virtual bool StartSensor(
+      const PlatformSensorConfiguration& configuration) = 0;
+  virtual void StopSensor() = 0;
 
   // Can be overriden to return the sensor maximum sampling frequency
   // value obtained from the platform if it is available. If platfrom
@@ -64,6 +67,10 @@ class DEVICE_GENERIC_SENSOR_EXPORT PlatformSensor
   void AddClient(Client*);
   void RemoveClient(Client*);
 
+  const mojo::ScopedSharedBufferMapping& shared_buffer_mapping() {
+    return shared_buffer_mapping_;
+  }
+
  protected:
   virtual ~PlatformSensor();
   PlatformSensor(mojom::SensorType type,
@@ -74,9 +81,6 @@ class DEVICE_GENERIC_SENSOR_EXPORT PlatformSensor
   using ReadingBuffer = SensorReadingSharedBuffer;
 
   virtual bool UpdateSensorInternal(const ConfigMap& configurations);
-  virtual bool StartSensor(
-      const PlatformSensorConfiguration& configuration) = 0;
-  virtual void StopSensor() = 0;
   virtual bool CheckSensorConfiguration(
       const PlatformSensorConfiguration& configuration) = 0;