arc-bridge: Implement IPC message for app launcher

components/arc/BUILD.gn

 # Copyright 2015 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.
 
 static_library("arc") {
   sources = [
     "arc_bridge_service.cc",
     "arc_bridge_service.h",
     "arc_bridge_service_impl.cc",
     "arc_bridge_service_impl.h",
     "common/arc_message_generator.cc",
+    "common/arc_message_traits.cc",
+    "common/arc_message_traits.h",
   ]
 
   deps = [
     "//base",
     "//chromeos",
     "//ipc",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "arc_bridge_service_unittest.cc",
   ]
 
   deps = [
     ":arc",
     "//base",
     "//chromeos",
     "//ipc",
     "//testing/gtest",
   ]
 }