[Sensors] Improvements in shared buffer managing

device/generic_sensor/public/cpp/sensor_reading.cc

+// 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.
+
+#include "device/generic_sensor/public/cpp/sensor_reading.h"
+
+namespace device {
+
+SensorReading::SensorReading() = default;
+SensorReading::SensorReading(const SensorReading& other) = default;
+SensorReading::~SensorReading() = default;
+
+SensorReadingSharedBuffer::SensorReadingSharedBuffer() = default;
+SensorReadingSharedBuffer::~SensorReadingSharedBuffer() = default;
+
+// static
+uint64_t SensorReadingSharedBuffer::GetOffset(mojom::SensorType type) {
+  return (static_cast<uint64_t>(mojom::SensorType::LAST) -
+          static_cast<uint64_t>(type)) *
+         sizeof(SensorReadingSharedBuffer);
+}
+
+}  // namespace device