remoting/host/cast_extension_session.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "remoting/host/cast_extension_session.h"
   6
   7 #include "base/bind.h"
   8 #include "base/json/json_reader.h"
   9 #include "base/json/json_writer.h"
  10 #include "base/logging.h"
  11 #include "base/synchronization/waitable_event.h"
  12 #include "net/url_request/url_request_context_getter.h"
  13 #include "remoting/host/cast_video_capturer_adapter.h"
  14 #include "remoting/host/chromium_port_allocator_factory.h"
  15 #include "remoting/host/client_session.h"
  16 #include "remoting/proto/control.pb.h"
  17 #include "remoting/protocol/client_stub.h"
  18 #include "third_party/libjingle/source/talk/app/webrtc/mediastreaminterface.h"
  19 #include "third_party/libjingle/source/talk/app/webrtc/test/fakeconstraints.h"
  20 #include "third_party/libjingle/source/talk/app/webrtc/videosourceinterface.h"
  21
  22 namespace remoting {
  23
  24 // Used as the type attribute of all Cast protocol::ExtensionMessages.
  25 const char kExtensionMessageType[] = "cast_message";
  26
  27 // Top-level keys used in all extension messages between host and client.
  28 // Must keep synced with webapp.
  29 const char kTopLevelData[] = "chromoting_data";
  30 const char kTopLevelSubject[] = "subject";
  31
  32 // Keys used to describe the subject of a cast extension message. WebRTC-related
  33 // message subjects are prepended with "webrtc_".
  34 // Must keep synced with webapp.
  35 const char kSubjectReady[] = "ready";
  36 const char kSubjectTest[] = "test";
  37 const char kSubjectNewCandidate[] = "webrtc_candidate";
  38 const char kSubjectOffer[] = "webrtc_offer";
  39 const char kSubjectAnswer[] = "webrtc_answer";
  40
  41 // WebRTC headers used inside messages with subject = "webrtc_*".
  42 const char kWebRtcCandidate[] = "candidate";
  43 const char kWebRtcSessionDescType[] = "type";
  44 const char kWebRtcSessionDescSDP[] = "sdp";
  45 const char kWebRtcSDPMid[] = "sdpMid";
  46 const char kWebRtcSDPMLineIndex[] = "sdpMLineIndex";
  47
  48 // Media labels used over the PeerConnection.
  49 const char kVideoLabel[] = "cast_video_label";
  50 const char kStreamLabel[] = "stream_label";
  51
  52 // Default STUN server used to construct
  53 // webrtc::PeerConnectionInterface::RTCConfiguration for the PeerConnection.
  54 const char kDefaultStunURI[] = "stun:stun.l.google.com:19302";
  55
  56 const char kWorkerThreadName[] = "CastExtensionSessionWorkerThread";
  57
  58 // Interval between each call to PollPeerConnectionStats().
  59 const int kStatsLogIntervalSec = 10;
  60
  61 // Minimum frame rate for video streaming over the PeerConnection in frames per
  62 // second, added as a media constraint when constructing the video source for
  63 // the Peer Connection.
  64 const int kMinFramesPerSecond = 5;
  65
  66 // A webrtc::SetSessionDescriptionObserver implementation used to receive the
  67 // results of setting local and remote descriptions of the PeerConnection.
  68 class CastSetSessionDescriptionObserver
  69     : public webrtc::SetSessionDescriptionObserver {
  70  public:
  71   static CastSetSessionDescriptionObserver* Create() {
  72     return new rtc::RefCountedObject<CastSetSessionDescriptionObserver>();
  73   }
  74   void OnSuccess() override {
  75     VLOG(1) << "Setting session description succeeded.";
  76   }
  77   void OnFailure(const std::string& error) override {
  78     LOG(ERROR) << "Setting session description failed: " << error;
  79   }
  80
  81  protected:
  82   CastSetSessionDescriptionObserver() {}
  83   ~CastSetSessionDescriptionObserver() override {}
  84
  85   DISALLOW_COPY_AND_ASSIGN(CastSetSessionDescriptionObserver);
  86 };
  87
  88 // A webrtc::CreateSessionDescriptionObserver implementation used to receive the
  89 // results of creating descriptions for this end of the PeerConnection.
  90 class CastCreateSessionDescriptionObserver
  91     : public webrtc::CreateSessionDescriptionObserver {
  92  public:
  93   static CastCreateSessionDescriptionObserver* Create(
  94       CastExtensionSession* session) {
  95     return new rtc::RefCountedObject<CastCreateSessionDescriptionObserver>(
  96         session);
  97   }
  98   void OnSuccess(webrtc::SessionDescriptionInterface* desc) override {
  99     if (cast_extension_session_ == nullptr) {
 100       LOG(ERROR)
 101           << "No CastExtensionSession. Creating session description succeeded.";
 102       return;
 103     }
 104     cast_extension_session_->OnCreateSessionDescription(desc);
 105   }
 106   void OnFailure(const std::string& error) override {
 107     if (cast_extension_session_ == nullptr) {
 108       LOG(ERROR)
 109           << "No CastExtensionSession. Creating session description failed.";
 110       return;
 111     }
 112     cast_extension_session_->OnCreateSessionDescriptionFailure(error);
 113   }
 114   void SetCastExtensionSession(CastExtensionSession* cast_extension_session) {
 115     cast_extension_session_ = cast_extension_session;
 116   }
 117
 118  protected:
 119   explicit CastCreateSessionDescriptionObserver(CastExtensionSession* session)
 120       : cast_extension_session_(session) {}
 121   ~CastCreateSessionDescriptionObserver() override {}
 122
 123  private:
 124   CastExtensionSession* cast_extension_session_;
 125
 126   DISALLOW_COPY_AND_ASSIGN(CastCreateSessionDescriptionObserver);
 127 };
 128
 129 // A webrtc::StatsObserver implementation used to receive statistics about the
 130 // current PeerConnection.
 131 class CastStatsObserver : public webrtc::StatsObserver {
 132  public:
 133   static CastStatsObserver* Create() {
 134     return new rtc::RefCountedObject<CastStatsObserver>();
 135   }
 136
 137   void OnComplete(const webrtc::StatsReports& reports) override {
 138     VLOG(1) << "Received " << reports.size() << " new StatsReports.";
 139
 140     int index = 0;
 141     for (const auto* report : reports) {
 142       VLOG(1) << "Report " << index++ << ":";
 143       for (const auto& v : report->values()) {
 144         VLOG(1) << "Stat: " << v->display_name() << "=" << v->value << ".";
 145       }
 146     }
 147   }
 148
 149  protected:
 150   CastStatsObserver() {}
 151   ~CastStatsObserver() override {}
 152
 153   DISALLOW_COPY_AND_ASSIGN(CastStatsObserver);
 154 };
 155
 156 // TODO(aiguha): Fix PeerConnnection-related tear down crash caused by premature
 157 // destruction of cricket::CaptureManager (which occurs on releasing
 158 // |peer_conn_factory_|). See crbug.com/403840.
 159 CastExtensionSession::~CastExtensionSession() {
 160   DCHECK(caller_task_runner_->BelongsToCurrentThread());
 161
 162   // Explicitly clear |create_session_desc_observer_|'s pointer to |this|,
 163   // since the CastExtensionSession is destructing. Otherwise,
 164   // |create_session_desc_observer_| would be left with a dangling pointer.
 165   create_session_desc_observer_->SetCastExtensionSession(nullptr);
 166
 167   CleanupPeerConnection();
 168 }
 169
 170 // static
 171 scoped_ptr<CastExtensionSession> CastExtensionSession::Create(
 172     scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner,
 173     scoped_refptr<net::URLRequestContextGetter> url_request_context_getter,
 174     const protocol::NetworkSettings& network_settings,
 175     ClientSessionControl* client_session_control,
 176     protocol::ClientStub* client_stub) {
 177   scoped_ptr<CastExtensionSession> cast_extension_session(
 178       new CastExtensionSession(caller_task_runner,
 179                                url_request_context_getter,
 180                                network_settings,
 181                                client_session_control,
 182                                client_stub));
 183   if (!cast_extension_session->WrapTasksAndSave() ||
 184       !cast_extension_session->InitializePeerConnection()) {
 185     return nullptr;
 186   }
 187   return cast_extension_session.Pass();
 188 }
 189
 190 void CastExtensionSession::OnCreateSessionDescription(
 191     webrtc::SessionDescriptionInterface* desc) {
 192   if (!caller_task_runner_->BelongsToCurrentThread()) {
 193     caller_task_runner_->PostTask(
 194         FROM_HERE,
 195         base::Bind(&CastExtensionSession::OnCreateSessionDescription,
 196                    base::Unretained(this),
 197                    desc));
 198     return;
 199   }
 200
 201   peer_connection_->SetLocalDescription(
 202       CastSetSessionDescriptionObserver::Create(), desc);
 203
 204   scoped_ptr<base::DictionaryValue> json(new base::DictionaryValue());
 205   json->SetString(kWebRtcSessionDescType, desc->type());
 206   std::string subject =
 207       (desc->type() == "offer") ? kSubjectOffer : kSubjectAnswer;
 208   std::string desc_str;
 209   desc->ToString(&desc_str);
 210   json->SetString(kWebRtcSessionDescSDP, desc_str);
 211   std::string json_str;
 212   if (!base::JSONWriter::Write(json.get(), &json_str)) {
 213     LOG(ERROR) << "Failed to serialize sdp message.";
 214     return;
 215   }
 216
 217   SendMessageToClient(subject.c_str(), json_str);
 218 }
 219
 220 void CastExtensionSession::OnCreateSessionDescriptionFailure(
 221     const std::string& error) {
 222   VLOG(1) << "Creating Session Description failed: " << error;
 223 }
 224
 225 // TODO(aiguha): Support the case(s) where we've grabbed the capturer already,
 226 // but another extension reset the video pipeline. We should remove the
 227 // stream from the peer connection here, and then attempt to re-setup the
 228 // peer connection in the OnRenegotiationNeeded() callback.
 229 // See crbug.com/403843.
 230 void CastExtensionSession::OnCreateVideoCapturer(
 231     scoped_ptr<webrtc::DesktopCapturer>* capturer) {
 232   if (has_grabbed_capturer_) {
 233     LOG(ERROR) << "The video pipeline was reset unexpectedly.";
 234     has_grabbed_capturer_ = false;
 235     peer_connection_->RemoveStream(stream_.release());
 236     return;
 237   }
 238
 239   if (received_offer_) {
 240     has_grabbed_capturer_ = true;
 241     if (SetupVideoStream(capturer->Pass())) {
 242       peer_connection_->CreateAnswer(create_session_desc_observer_, nullptr);
 243     } else {
 244       has_grabbed_capturer_ = false;
 245       // Ignore the received offer, since we failed to setup a video stream.
 246       received_offer_ = false;
 247     }
 248     return;
 249   }
 250 }
 251
 252 bool CastExtensionSession::ModifiesVideoPipeline() const {
 253   return true;
 254 }
 255
 256 // Returns true if the |message| is a Cast ExtensionMessage, even if
 257 // it was badly formed or a resulting action failed. This is done so that
 258 // the host does not continue to attempt to pass |message| to other
 259 // HostExtensionSessions.
 260 bool CastExtensionSession::OnExtensionMessage(
 261     ClientSessionControl* client_session_control,
 262     protocol::ClientStub* client_stub,
 263     const protocol::ExtensionMessage& message) {
 264   if (message.type() != kExtensionMessageType) {
 265     return false;
 266   }
 267
 268   scoped_ptr<base::Value> value(base::JSONReader::Read(message.data()));
 269   base::DictionaryValue* client_message;
 270   if (!(value && value->GetAsDictionary(&client_message))) {
 271     LOG(ERROR) << "Could not read cast extension message.";
 272     return true;
 273   }
 274
 275   std::string subject;
 276   if (!client_message->GetString(kTopLevelSubject, &subject)) {
 277     LOG(ERROR) << "Invalid Cast Extension Message (missing subject header).";
 278     return true;
 279   }
 280
 281   if (subject == kSubjectOffer && !received_offer_) {
 282     // Reset the video pipeline so we can grab the screen capturer and setup
 283     // a video stream.
 284     if (ParseAndSetRemoteDescription(client_message)) {
 285       received_offer_ = true;
 286       LOG(INFO) << "About to ResetVideoPipeline.";
 287       client_session_control_->ResetVideoPipeline();
 288
 289     }
 290   } else if (subject == kSubjectAnswer) {
 291     ParseAndSetRemoteDescription(client_message);
 292   } else if (subject == kSubjectNewCandidate) {
 293     ParseAndAddICECandidate(client_message);
 294   } else {
 295     VLOG(1) << "Unexpected CastExtension Message: " << message.data();
 296   }
 297   return true;
 298 }
 299
 300 // Private methods ------------------------------------------------------------
 301
 302 CastExtensionSession::CastExtensionSession(
 303     scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner,
 304     scoped_refptr<net::URLRequestContextGetter> url_request_context_getter,
 305     const protocol::NetworkSettings& network_settings,
 306     ClientSessionControl* client_session_control,
 307     protocol::ClientStub* client_stub)
 308     : caller_task_runner_(caller_task_runner),
 309       url_request_context_getter_(url_request_context_getter),
 310       network_settings_(network_settings),
 311       client_session_control_(client_session_control),
 312       client_stub_(client_stub),
 313       stats_observer_(CastStatsObserver::Create()),
 314       received_offer_(false),
 315       has_grabbed_capturer_(false),
 316       signaling_thread_wrapper_(nullptr),
 317       worker_thread_wrapper_(nullptr),
 318       worker_thread_(kWorkerThreadName) {
 319   DCHECK(caller_task_runner_->BelongsToCurrentThread());
 320   DCHECK(url_request_context_getter_.get());
 321   DCHECK(client_session_control_);
 322   DCHECK(client_stub_);
 323
 324   // The worker thread is created with base::MessageLoop::TYPE_IO because
 325   // the PeerConnection performs some port allocation operations on this thread
 326   // that require it. See crbug.com/404013.
 327   base::Thread::Options options(base::MessageLoop::TYPE_IO, 0);
 328   worker_thread_.StartWithOptions(options);
 329   worker_task_runner_ = worker_thread_.task_runner();
 330 }
 331
 332 bool CastExtensionSession::ParseAndSetRemoteDescription(
 333     base::DictionaryValue* message) {
 334   DCHECK(peer_connection_.get() != nullptr);
 335
 336   base::DictionaryValue* message_data;
 337   if (!message->GetDictionary(kTopLevelData, &message_data)) {
 338     LOG(ERROR) << "Invalid Cast Extension Message (missing data).";
 339     return false;
 340   }
 341
 342   std::string webrtc_type;
 343   if (!message_data->GetString(kWebRtcSessionDescType, &webrtc_type)) {
 344     LOG(ERROR)
 345         << "Invalid Cast Extension Message (missing webrtc type header).";
 346     return false;
 347   }
 348
 349   std::string sdp;
 350   if (!message_data->GetString(kWebRtcSessionDescSDP, &sdp)) {
 351     LOG(ERROR) << "Invalid Cast Extension Message (missing webrtc sdp header).";
 352     return false;
 353   }
 354
 355   webrtc::SdpParseError error;
 356   webrtc::SessionDescriptionInterface* session_description(
 357       webrtc::CreateSessionDescription(webrtc_type, sdp, &error));
 358
 359   if (!session_description) {
 360     LOG(ERROR) << "Invalid Cast Extension Message (could not parse sdp).";
 361     VLOG(1) << "SdpParseError was: " << error.description;
 362     return false;
 363   }
 364
 365   peer_connection_->SetRemoteDescription(
 366       CastSetSessionDescriptionObserver::Create(), session_description);
 367   return true;
 368 }
 369
 370 bool CastExtensionSession::ParseAndAddICECandidate(
 371     base::DictionaryValue* message) {
 372   DCHECK(peer_connection_.get() != nullptr);
 373
 374   base::DictionaryValue* message_data;
 375   if (!message->GetDictionary(kTopLevelData, &message_data)) {
 376     LOG(ERROR) << "Invalid Cast Extension Message (missing data).";
 377     return false;
 378   }
 379
 380   std::string candidate_str;
 381   std::string sdp_mid;
 382   int sdp_mlineindex = 0;
 383   if (!message_data->GetString(kWebRtcSDPMid, &sdp_mid) ||
 384       !message_data->GetInteger(kWebRtcSDPMLineIndex, &sdp_mlineindex) ||
 385       !message_data->GetString(kWebRtcCandidate, &candidate_str)) {
 386     LOG(ERROR) << "Invalid Cast Extension Message (could not parse).";
 387     return false;
 388   }
 389
 390   rtc::scoped_ptr<webrtc::IceCandidateInterface> candidate(
 391       webrtc::CreateIceCandidate(sdp_mid, sdp_mlineindex, candidate_str));
 392   if (!candidate.get()) {
 393     LOG(ERROR)
 394         << "Invalid Cast Extension Message (could not create candidate).";
 395     return false;
 396   }
 397
 398   if (!peer_connection_->AddIceCandidate(candidate.get())) {
 399     LOG(ERROR) << "Failed to apply received ICE Candidate to PeerConnection.";
 400     return false;
 401   }
 402
 403   VLOG(1) << "Received and Added ICE Candidate: " << candidate_str;
 404
 405   return true;
 406 }
 407
 408 bool CastExtensionSession::SendMessageToClient(const std::string& subject,
 409                                                const std::string& data) {
 410   DCHECK(caller_task_runner_->BelongsToCurrentThread());
 411
 412   if (client_stub_ == nullptr) {
 413     LOG(ERROR) << "No Client Stub. Cannot send message to client.";
 414     return false;
 415   }
 416
 417   base::DictionaryValue message_dict;
 418   message_dict.SetString(kTopLevelSubject, subject);
 419   message_dict.SetString(kTopLevelData, data);
 420   std::string message_json;
 421
 422   if (!base::JSONWriter::Write(&message_dict, &message_json)) {
 423     LOG(ERROR) << "Failed to serialize JSON message.";
 424     return false;
 425   }
 426
 427   protocol::ExtensionMessage message;
 428   message.set_type(kExtensionMessageType);
 429   message.set_data(message_json);
 430   client_stub_->DeliverHostMessage(message);
 431   return true;
 432 }
 433
 434 void CastExtensionSession::EnsureTaskAndSetSend(rtc::Thread** ptr,
 435                                                 base::WaitableEvent* event) {
 436   jingle_glue::JingleThreadWrapper::EnsureForCurrentMessageLoop();
 437   jingle_glue::JingleThreadWrapper::current()->set_send_allowed(true);
 438   *ptr = jingle_glue::JingleThreadWrapper::current();
 439
 440   if (event != nullptr) {
 441     event->Signal();
 442   }
 443 }
 444
 445 bool CastExtensionSession::WrapTasksAndSave() {
 446   DCHECK(caller_task_runner_->BelongsToCurrentThread());
 447
 448   EnsureTaskAndSetSend(&signaling_thread_wrapper_);
 449   if (signaling_thread_wrapper_ == nullptr)
 450     return false;
 451
 452   base::WaitableEvent wrap_worker_thread_event(true, false);
 453   worker_task_runner_->PostTask(
 454       FROM_HERE,
 455       base::Bind(&CastExtensionSession::EnsureTaskAndSetSend,
 456                  base::Unretained(this),
 457                  &worker_thread_wrapper_,
 458                  &wrap_worker_thread_event));
 459   wrap_worker_thread_event.Wait();
 460
 461   return (worker_thread_wrapper_ != nullptr);
 462 }
 463
 464 bool CastExtensionSession::InitializePeerConnection() {
 465   DCHECK(caller_task_runner_->BelongsToCurrentThread());
 466   DCHECK(!peer_conn_factory_);
 467   DCHECK(!peer_connection_);
 468   DCHECK(worker_thread_wrapper_ != nullptr);
 469   DCHECK(signaling_thread_wrapper_ != nullptr);
 470
 471   peer_conn_factory_ = webrtc::CreatePeerConnectionFactory(
 472       worker_thread_wrapper_, signaling_thread_wrapper_, nullptr, nullptr,
 473       nullptr);
 474
 475   if (!peer_conn_factory_.get()) {
 476     CleanupPeerConnection();
 477     return false;
 478   }
 479
 480   VLOG(1) << "Created PeerConnectionFactory successfully.";
 481
 482   webrtc::PeerConnectionInterface::IceServers servers;
 483   webrtc::PeerConnectionInterface::IceServer server;
 484   server.uri = kDefaultStunURI;
 485   servers.push_back(server);
 486   webrtc::PeerConnectionInterface::RTCConfiguration rtc_config;
 487   rtc_config.servers = servers;
 488
 489   // DTLS-SRTP is the preferred encryption method. If set to kValueFalse, the
 490   // peer connection uses SDES. Disabling SDES as well will cause the peer
 491   // connection to fail to connect.
 492   // Note: For protection and unprotection of SRTP packets, the libjingle
 493   // ENABLE_EXTERNAL_AUTH flag must not be set.
 494   webrtc::FakeConstraints constraints;
 495   constraints.AddMandatory(webrtc::MediaConstraintsInterface::kEnableDtlsSrtp,
 496                            webrtc::MediaConstraintsInterface::kValueTrue);
 497
 498   rtc::scoped_refptr<webrtc::PortAllocatorFactoryInterface>
 499       port_allocator_factory = ChromiumPortAllocatorFactory::Create(
 500           network_settings_, url_request_context_getter_);
 501
 502   peer_connection_ = peer_conn_factory_->CreatePeerConnection(
 503       rtc_config, &constraints, port_allocator_factory, nullptr, this);
 504
 505   if (!peer_connection_.get()) {
 506     CleanupPeerConnection();
 507     return false;
 508   }
 509
 510   VLOG(1) << "Created PeerConnection successfully.";
 511
 512   create_session_desc_observer_ =
 513       CastCreateSessionDescriptionObserver::Create(this);
 514
 515   // Send a test message to the client. Then, notify the client to start
 516   // webrtc offer/answer negotiation.
 517   if (!SendMessageToClient(kSubjectTest, "Hello, client.") ||
 518       !SendMessageToClient(kSubjectReady, "Host ready to receive offers.")) {
 519     LOG(ERROR) << "Failed to send messages to client.";
 520     return false;
 521   }
 522
 523   return true;
 524 }
 525
 526 bool CastExtensionSession::SetupVideoStream(
 527     scoped_ptr<webrtc::DesktopCapturer> desktop_capturer) {
 528   DCHECK(caller_task_runner_->BelongsToCurrentThread());
 529   DCHECK(desktop_capturer);
 530
 531   if (stream_) {
 532     VLOG(1) << "Already added MediaStream. Aborting Setup.";
 533     return false;
 534   }
 535
 536   scoped_ptr<CastVideoCapturerAdapter> cast_video_capturer_adapter(
 537       new CastVideoCapturerAdapter(desktop_capturer.Pass()));
 538
 539   // Set video stream constraints.
 540   webrtc::FakeConstraints video_constraints;
 541   video_constraints.AddMandatory(
 542       webrtc::MediaConstraintsInterface::kMinFrameRate, kMinFramesPerSecond);
 543
 544   rtc::scoped_refptr<webrtc::VideoTrackInterface> video_track =
 545       peer_conn_factory_->CreateVideoTrack(
 546           kVideoLabel,
 547           peer_conn_factory_->CreateVideoSource(
 548               cast_video_capturer_adapter.release(), &video_constraints));
 549
 550   stream_ = peer_conn_factory_->CreateLocalMediaStream(kStreamLabel);
 551
 552   if (!stream_->AddTrack(video_track) ||
 553       !peer_connection_->AddStream(stream_)) {
 554     return false;
 555   }
 556
 557   VLOG(1) << "Setup video stream successfully.";
 558
 559   return true;
 560 }
 561
 562 void CastExtensionSession::PollPeerConnectionStats() {
 563   if (!connection_active()) {
 564     VLOG(1) << "Cannot poll stats while PeerConnection is inactive.";
 565   }
 566   rtc::scoped_refptr<webrtc::MediaStreamTrackInterface> video_track =
 567       stream_->FindVideoTrack(kVideoLabel);
 568   peer_connection_->GetStats(
 569       stats_observer_,
 570       video_track.release(),
 571       webrtc::PeerConnectionInterface::kStatsOutputLevelStandard);
 572 }
 573
 574 void CastExtensionSession::CleanupPeerConnection() {
 575   peer_connection_->Close();
 576   peer_connection_ = nullptr;
 577   stream_ = nullptr;
 578   peer_conn_factory_ = nullptr;
 579   worker_thread_.Stop();
 580 }
 581
 582 bool CastExtensionSession::connection_active() const {
 583   return peer_connection_.get() != nullptr;
 584 }
 585
 586 // webrtc::PeerConnectionObserver implementation -------------------------------
 587 void CastExtensionSession::OnSignalingChange(
 588     webrtc::PeerConnectionInterface::SignalingState new_state) {
 589   VLOG(1) << "PeerConnectionObserver: SignalingState changed to:" << new_state;
 590 }
 591
 592 void CastExtensionSession::OnStateChange(
 593     webrtc::PeerConnectionObserver::StateType state_changed) {
 594   VLOG(1) << "PeerConnectionObserver: StateType changed to: " << state_changed;
 595 }
 596
 597 void CastExtensionSession::OnAddStream(webrtc::MediaStreamInterface* stream) {
 598   VLOG(1) << "PeerConnectionObserver: stream added: " << stream->label();
 599 }
 600
 601 void CastExtensionSession::OnRemoveStream(
 602     webrtc::MediaStreamInterface* stream) {
 603   VLOG(1) << "PeerConnectionObserver: stream removed: " << stream->label();
 604 }
 605
 606 void CastExtensionSession::OnDataChannel(
 607     webrtc::DataChannelInterface* data_channel) {
 608   VLOG(1) << "PeerConnectionObserver: data channel: " << data_channel->label();
 609 }
 610
 611 void CastExtensionSession::OnRenegotiationNeeded() {
 612   VLOG(1) << "PeerConnectionObserver: renegotiation needed.";
 613 }
 614
 615 void CastExtensionSession::OnIceConnectionChange(
 616     webrtc::PeerConnectionInterface::IceConnectionState new_state) {
 617   VLOG(1) << "PeerConnectionObserver: IceConnectionState changed to: "
 618           << new_state;
 619
 620   // TODO(aiguha): Maybe start timer only if enabled by command-line flag or
 621   // at a particular verbosity level.
 622   if (!stats_polling_timer_.IsRunning() &&
 623       new_state == webrtc::PeerConnectionInterface::kIceConnectionConnected) {
 624     stats_polling_timer_.Start(
 625         FROM_HERE,
 626         base::TimeDelta::FromSeconds(kStatsLogIntervalSec),
 627         this,
 628         &CastExtensionSession::PollPeerConnectionStats);
 629   }
 630 }
 631
 632 void CastExtensionSession::OnIceGatheringChange(
 633     webrtc::PeerConnectionInterface::IceGatheringState new_state) {
 634   VLOG(1) << "PeerConnectionObserver: IceGatheringState changed to: "
 635           << new_state;
 636 }
 637
 638 void CastExtensionSession::OnIceComplete() {
 639   VLOG(1) << "PeerConnectionObserver: all ICE candidates found.";
 640 }
 641
 642 void CastExtensionSession::OnIceCandidate(
 643     const webrtc::IceCandidateInterface* candidate) {
 644   std::string candidate_str;
 645   if (!candidate->ToString(&candidate_str)) {
 646     LOG(ERROR) << "PeerConnectionObserver: failed to serialize candidate.";
 647     return;
 648   }
 649   scoped_ptr<base::DictionaryValue> json(new base::DictionaryValue());
 650   json->SetString(kWebRtcSDPMid, candidate->sdp_mid());
 651   json->SetInteger(kWebRtcSDPMLineIndex, candidate->sdp_mline_index());
 652   json->SetString(kWebRtcCandidate, candidate_str);
 653   std::string json_str;
 654   if (!base::JSONWriter::Write(json.get(), &json_str)) {
 655     LOG(ERROR) << "Failed to serialize candidate message.";
 656     return;
 657   }
 658   SendMessageToClient(kSubjectNewCandidate, json_str);
 659 }
 660
 661 }  // namespace remoting