[Media Router] Support dual discovery

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

 // Copyright 2017 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_media_sink_service_proxy.h"
 
 #include "chrome/browser/media/router/discovery/dial/dial_media_sink_service_impl.h"
 #include "content/public/browser/browser_context.h"
 
 using content::BrowserThread;
 
 namespace media_router {
 
 DialMediaSinkServiceProxy::DialMediaSinkServiceProxy(
     const MediaSinkService::OnSinksDiscoveredCallback& callback,
     content::BrowserContext* context)
-    : MediaSinkService(callback) {
+    : MediaSinkService(callback), observer_(nullptr) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   auto* profile = Profile::FromBrowserContext(context);
   request_context_ = profile->GetRequestContext();
   DCHECK(request_context_);
 }
 
 DialMediaSinkServiceProxy::~DialMediaSinkServiceProxy() = default;
 
 void DialMediaSinkServiceProxy::Start() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   content::BrowserThread::PostTask(
       content::BrowserThread::IO, FROM_HERE,
       base::Bind(&DialMediaSinkServiceProxy::StartOnIOThread, this));
 }
 
 void DialMediaSinkServiceProxy::Stop() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   content::BrowserThread::PostTask(
       content::BrowserThread::IO, FROM_HERE,
       base::Bind(&DialMediaSinkServiceProxy::StopOnIOThread, this));
 }
 
+void DialMediaSinkServiceProxy::AddObserver(Observer* observer) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DCHECK(observer);
+  observer_ = observer;
+}
+
+void DialMediaSinkServiceProxy::RemoveObserver(Observer* observer) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DCHECK(observer);
+  if (dial_media_sink_service_)
+    dial_media_sink_service_->RemoveObserver(observer);
+
+  observer_ = nullptr;
+}
+
 void DialMediaSinkServiceProxy::SetDialMediaSinkServiceForTest(
     std::unique_ptr<DialMediaSinkServiceImpl> dial_media_sink_service) {
   DCHECK(dial_media_sink_service);
   DCHECK(!dial_media_sink_service_);
   dial_media_sink_service_ = std::move(dial_media_sink_service);
 }
 
 void DialMediaSinkServiceProxy::StartOnIOThread() {
   if (!dial_media_sink_service_) {
     // Need to explicitly delete |dial_media_sink_service_| outside dtor to
     // avoid circular dependency.
     dial_media_sink_service_ = base::MakeUnique<DialMediaSinkServiceImpl>(
         base::Bind(&DialMediaSinkServiceProxy::OnSinksDiscoveredOnIOThread,
                    this),
         request_context_.get());
+    if (observer_)
+      dial_media_sink_service_->AddObserver(observer_);
   }
 
   dial_media_sink_service_->Start();
 }
 
 void DialMediaSinkServiceProxy::StopOnIOThread() {
   if (!dial_media_sink_service_)
     return;
 
   dial_media_sink_service_->Stop();
   dial_media_sink_service_.reset();
 }
 
 void DialMediaSinkServiceProxy::OnSinksDiscoveredOnIOThread(
     std::vector<MediaSinkInternal> sinks) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   content::BrowserThread::PostTask(
       content::BrowserThread::UI, FROM_HERE,
       base::Bind(sink_discovery_callback_, std::move(sinks)));
 }
 
 }  // namespace media_router