Revert 221619 "Initial chrome.mdns API."

trunk/src/chrome/browser/extensions/api/mdns/dns_sd_registry.cc

-// Copyright 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 "chrome/browser/extensions/api/mdns/dns_sd_registry.h"
-
-namespace extensions {
-
-DnsSdRegistry::DnsSdRegistry() {}
-DnsSdRegistry::~DnsSdRegistry() {}
-
-void DnsSdRegistry::AddObserver(DnsSdObserver* observer) {
-  observers_.AddObserver(observer);
-}
-
-void DnsSdRegistry::RemoveObserver(DnsSdObserver* observer) {
-  observers_.RemoveObserver(observer);
-}
-
-void DnsSdRegistry::RegisterDnsSdListener(std::string service_type) {
-  // TODO(mfoltz): Start DNS-SD service.
-}
-
-void DnsSdRegistry::UnregisterDnsSdListener(std::string service_type) {
-  // TODO(mfoltz): Stop DNS-SD service.
-}
-
-}  // namespace extensions