nfc: Add native NFC API definitions.

device/nfc/nfc_adapter_factory.cc

+// Copyright (c) 2013 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.
+
+#include "device/nfc/nfc_adapter_factory.h"
+
+#include "base/lazy_instance.h"
+#include "base/memory/weak_ptr.h"
+
+namespace device {
+
+// static
+bool NfcAdapterFactory::IsNfcAvailable() {
+  // TODO(armansito): Return true on supported platforms here.
+  return false;
+}
+
+// static
+void NfcAdapterFactory::GetAdapter(const AdapterCallback& /* callback */) {
+  // TODO(armansito): Create platform-specific implementation instances here.
+  // No platform currently supports NFC, so we never invoke the callback.
+}
+
+}  // namespace device