[Sensors] Improvements in shared buffer managing

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 0485fc6861fcc2bd68dbcd30970dee2c1ecc8113..2ec1d5200195c3660a41b3c0c0416de5ba8da205 100644
--- a/device/generic_sensor/platform_sensor.h
+++ b/device/generic_sensor/platform_sensor.h
@@ -12,6 +12,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
+#include "device/base/synchronization/shared_memory_seqlock_buffer.h"
 #include "device/generic_sensor/public/interfaces/sensor.mojom.h"
 #include "mojo/public/cpp/system/buffer.h"
 
@@ -50,6 +51,12 @@ class PlatformSensor : public base::RefCountedThreadSafe<PlatformSensor> {
   void RemoveClient(Client*);
 
  protected:
+  using ReadingBuffer = SharedMemorySeqLockBuffer<mojom::SensorReading>;
+
+ public:
+  static const size_t kReadingBufferSize = sizeof(ReadingBuffer);
+
+ protected:
   virtual ~PlatformSensor();
   PlatformSensor(mojom::SensorType type,
                  mojo::ScopedSharedBufferMapping mapping,
@@ -64,17 +71,19 @@ class PlatformSensor : public base::RefCountedThreadSafe<PlatformSensor> {
   virtual bool CheckSensorConfiguration(
       const PlatformSensorConfiguration& configuration) = 0;
 
+  // Updates shared buffer with new sensor reading data.
+  // Note: this method is thread-safe.
+  void UpdateSensorReading(const mojom::SensorReading& reading);
+
   void NotifySensorReadingChanged();
   void NotifySensorError();
 
-  mojo::ScopedSharedBufferMapping shared_buffer_mapping_;
-
   // For testing purposes.
   const ConfigMap& config_map() const { return config_map_; }
 
  private:
   friend class base::RefCountedThreadSafe<PlatformSensor>;
-
+  mojo::ScopedSharedBufferMapping shared_buffer_mapping_;
   mojom::SensorType type_;
   base::ObserverList<Client, true> clients_;
   ConfigMap config_map_;