[Sensors] Improvements in shared buffer managing

device/generic_sensor/public/cpp/sensor_reading.cc

Index: device/generic_sensor/public/cpp/sensor_reading.cc
diff --git a/device/generic_sensor/public/cpp/sensor_reading.cc b/device/generic_sensor/public/cpp/sensor_reading.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ae61145f4d6566e1817c2fe9143e248b3ed15859
--- /dev/null
+++ b/device/generic_sensor/public/cpp/sensor_reading.cc
@@ -0,0 +1,23 @@
+// 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