Add ProtoDecoder for sending messages between Host and Controller when pairing

components/pairing/BUILD.gn

 # Copyright 2014 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("//third_party/protobuf/proto_library.gni")
 
 source_set("pairing") {
   sources = [
     "pairing/fake_controller_pairing_controller.cc",
     "pairing/fake_controller_pairing_controller.h",
     "pairing/fake_host_pairing_controller.cc",
     "pairing/fake_host_pairing_controller.h",
     "pairing/controller_pairing_controller.cc",
     "pairing/controller_pairing_controller.h",
     "pairing/host_pairing_controller.cc",
     "pairing/host_pairing_controller.h",
     "pairing/message_buffer.cc",
     "pairing/message_buffer.h",
+    "pairing/proto_decoder.cc",
+    "pairing/proto_decoder.h",
   ]
 
   deps = [
     "//base",
     "//device/bluetooth",
     "//net",
   ]
 }
 
 source_set("unit_tests") {
   sources = [
     "message_buffer_unittest.cc",
   ]
 
   deps = [
     ":pairing",
     "//testing/gtest",
   ]
 }
 
 proto_library("proto") {
   sources = [
     "pairing_api.proto",
   ]
   'proto_in_dir' = 'pairing'
   'proto_out_dir' = 'components/pairing'
 }