Port device_generic_sensor to be hosted in Device Service.

services/device/public/cpp/BUILD.gn

Index: services/device/public/cpp/BUILD.gn
diff --git a/services/device/public/cpp/BUILD.gn b/services/device/public/cpp/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..e9ebe278f990b1f3b38f962fd18c9cd4d0998804
--- /dev/null
+++ b/services/device/public/cpp/BUILD.gn
@@ -0,0 +1,17 @@
+# 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.
+
+import("//build/config/features.gni")
+
+source_set("device_features") {
+  public = [
+    "device_features.h",
+  ]
+  sources = [
+    "device_features.cc",
+  ]
+  public_deps = [
+    "//base",
+  ]
+}