[webnfc] Add default implementation for nfc mojo service.

device/nfc/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("//build/config/features.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
 static_library("nfc") {
   sources = [
     "nfc_adapter.cc",
@@ skipping 26 matching lines @@
   ]
 
   if (is_chromeos) {
     deps += [
       "//chromeos",
       "//dbus",
     ]
   }
 }
 
+component("nfc_mojo") {
+  sources = [
+    "nfc_export.h",
+    "nfc_impl.h",
+    "nfc_impl_default.cc",
+  ]
+
+  defines = [ "DEVICE_NFC_IMPLEMENTATION" ]
+
+  deps = [
+    ":mojo_bindings",
+    "//base",
+    "//mojo/edk/system",
+    "//mojo/public/cpp/bindings",
+  ]
+}
+
 mojom("mojo_bindings") {
   sources = [
     "nfc.mojom",
   ]
 }