chromeos: adds TouchDeviceServer and wires up in mushrome

services/ui/input_devices/BUILD.gn

 # 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.
 
 import("//testing/test.gni")
 
 source_set("input_devices") {
   sources = [
     "input_device_server.cc",
     "input_device_server.h",
   ]
 
   deps = [
     "//base",
     "//services/service_manager/public/cpp",
     "//ui/events/devices",
   ]
 
   public_deps = [
     "//services/ui/public/interfaces/input_devices",
   ]
+
+  if (is_chromeos) {
+    sources += [
+      "touch_device_server.cc",
+      "touch_device_server.h",
+    ]
+  }
 }
 
 source_set("tests") {
   testonly = true
 
   sources = [
     "input_device_unittests.cc",
   ]
 
   deps = [
     ":input_devices",
     "//base",
     "//base/test:test_support",
     "//services/service_manager/public/cpp",
     "//services/service_manager/public/cpp:service_test_support",
     "//services/ui/public/cpp/input_devices",
     "//services/ui/public/interfaces/input_devices",
     "//testing/gtest",
     "//ui/events/devices",
   ]
 }