Port device_generic_sensor to be hosted in Device Service.

services/device/public/cpp/device_features.h

+// Copyright 2017 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.
+
+// This file defines all the public base::FeatureList features for the
+// services/device module.
+
+#ifndef SERVICES_DEVICE_PUBLIC_CPP_DEVICE_FEATURES_H_
+#define SERVICES_DEVICE_PUBLIC_CPP_DEVICE_FEATURES_H_
+
+#include "base/feature_list.h"
+
+namespace features {
+
+// The features should be documented alongside the definition of their values
+// in the .cc file.
+extern const base::Feature kGenericSensor;
+
+}  // namespace features
+
+#endif  // SERVICES_DEVICE_PUBLIC_CPP_DEVICE_FEATURES_H_