[Media Router] Add DialMediaSinkService and DeviceDescriptionService

chrome/browser/media/router/discovery/dial/dial_registry.cc

 // Copyright (c) 2012 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/media/router/discovery/dial/dial_registry.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
@@ skipping 108 matching lines @@
 void DialRegistry::AddDeviceForTest(const DialDeviceData& device_data) {
   std::unique_ptr<DialDeviceData> test_data =
       base::MakeUnique<DialDeviceData>(device_data);
   device_by_label_map_.insert(
       std::make_pair(device_data.label(), test_data.get()));
   device_by_id_map_.insert(
       std::make_pair(device_data.device_id(), std::move(test_data)));
 }
 
 bool DialRegistry::ReadyToDiscover() {
-  if (num_listeners_ == 0) {
+  if (!observers_.might_have_observers()) {
     OnDialError(DIAL_NO_LISTENERS);
     return false;
   }
   if (NetworkChangeNotifier::IsOffline()) {
     OnDialError(DIAL_NETWORK_DISCONNECTED);
     return false;
   }
   if (NetworkChangeNotifier::IsConnectionCellular(
           NetworkChangeNotifier::GetConnectionType())) {
     OnDialError(DIAL_CELLULAR_NETWORK);
@@ skipping 242 matching lines @@
   for (auto& observer : observers_)
     observer.OnDialDeviceEvent(devices);
 }
 
 void DialRegistry::OnDialError(DialErrorCode type) {
   for (auto& observer : observers_)
     observer.OnDialError(type);
 }
 
 }  // namespace media_router