Make rendering of MediaStreams reflect changes to its set of tracks.

content/renderer/media/webmediaplayer_ms.cc

Index: content/renderer/media/webmediaplayer_ms.cc
diff --git a/content/renderer/media/webmediaplayer_ms.cc b/content/renderer/media/webmediaplayer_ms.cc
index 87ab3a76d4a1cf3a8955c03bcba9ae0d386eed61..e9c0723231b4665afebf03e9c7f84eca6dfa432e 100644
--- a/content/renderer/media/webmediaplayer_ms.cc
+++ b/content/renderer/media/webmediaplayer_ms.cc
@@ -20,6 +20,8 @@
 #include "content/public/renderer/media_stream_audio_renderer.h"
 #include "content/public/renderer/media_stream_renderer_factory.h"
 #include "content/public/renderer/media_stream_video_renderer.h"
+#include "content/renderer/media/media_stream_audio_track.h"
+#include "content/renderer/media/media_stream_video_track.h"
 #include "content/renderer/media/web_media_element_source_utils.h"
 #include "content/renderer/media/webmediaplayer_ms_compositor.h"
 #include "content/renderer/media/webrtc_logging.h"
@@ -39,6 +41,14 @@
 #include "third_party/WebKit/public/platform/WebSize.h"
 #include "third_party/WebKit/public/web/WebLocalFrame.h"
 
+namespace {
+enum class RendererReloadAction {
+  KEEP_RENDERER,
+  REMOVE_RENDERER,
+  NEW_RENDERER
+};
+}  // namespace
+
 namespace content {
 
 // FrameDeliverer is responsible for delivering frames received on
@@ -191,6 +201,12 @@ WebMediaPlayerMS::~WebMediaPlayerMS() {
   DVLOG(1) << __func__;
   DCHECK(thread_checker_.CalledOnValidThread());
 
+  if (!web_stream_.IsNull()) {
+    MediaStream* native_stream = MediaStream::GetMediaStream(web_stream_);
+    if (native_stream)
+      native_stream->RemoveObserver(this);
+  }
+
   // Destruct compositor resources in the proper order.
   get_client()->SetWebLayer(nullptr);
   if (video_weblayer_)
@@ -224,24 +240,29 @@ void WebMediaPlayerMS::Load(LoadType load_type,
   // TODO(acolwell): Change this to DCHECK_EQ(load_type, LoadTypeMediaStream)
   // once Blink-side changes land.
   DCHECK_NE(load_type, kLoadTypeMediaSource);
-  blink::WebMediaStream web_stream =
-      GetWebMediaStreamFromWebMediaPlayerSource(source);
+  web_stream_ = GetWebMediaStreamFromWebMediaPlayerSource(source);
+  if (!web_stream_.IsNull()) {
+    MediaStream* native_stream = MediaStream::GetMediaStream(web_stream_);
+    if (native_stream)
+      native_stream->AddObserver(this);
+  }
 
   compositor_ = new WebMediaPlayerMSCompositor(
-      compositor_task_runner_, io_task_runner_, web_stream, AsWeakPtr());
+      compositor_task_runner_, io_task_runner_, web_stream_, AsWeakPtr());
 
   SetNetworkState(WebMediaPlayer::kNetworkStateLoading);
   SetReadyState(WebMediaPlayer::kReadyStateHaveNothing);
   std::string stream_id =
-      web_stream.IsNull() ? std::string() : web_stream.Id().Utf8();
+      web_stream_.IsNull() ? std::string() : web_stream_.Id().Utf8();
   media_log_->AddEvent(media_log_->CreateLoadEvent(stream_id));
 
   frame_deliverer_.reset(new WebMediaPlayerMS::FrameDeliverer(
       AsWeakPtr(),
       base::Bind(&WebMediaPlayerMSCompositor::EnqueueFrame, compositor_)));
   video_frame_provider_ = renderer_factory_->GetVideoRenderer(
-      web_stream, media::BindToCurrentLoop(base::Bind(
-                      &WebMediaPlayerMS::OnSourceError, AsWeakPtr())),
+      web_stream_,
+      media::BindToCurrentLoop(
+          base::Bind(&WebMediaPlayerMS::OnSourceError, AsWeakPtr())),
       frame_deliverer_->GetRepaintCallback(), io_task_runner_,
       media_task_runner_, worker_task_runner_, gpu_factories_);
 
@@ -258,7 +279,7 @@ void WebMediaPlayerMS::Load(LoadType load_type,
   }
 
   audio_renderer_ = renderer_factory_->GetAudioRenderer(
-      web_stream, routing_id, initial_audio_output_device_id_,
+      web_stream_, routing_id, initial_audio_output_device_id_,
       initial_security_origin_);
 
   if (!audio_renderer_)
@@ -272,10 +293,27 @@ void WebMediaPlayerMS::Load(LoadType load_type,
   if (audio_renderer_) {
     audio_renderer_->SetVolume(volume_);
     audio_renderer_->Start();
+
+    // Store the ID of audio track being played in |current_video_track_id_|
+    blink::WebVector<blink::WebMediaStreamTrack> audio_tracks;
+    if (!web_stream_.IsNull()) {
+      web_stream_.AudioTracks(audio_tracks);
+      DCHECK_GT(audio_tracks.size(), 0U);
+      current_audio_track_id_ = audio_tracks[0].Id();
+    }
   }
-  if (video_frame_provider_)
+
+  if (video_frame_provider_) {
     video_frame_provider_->Start();
 
+    // Store the ID of video track being played in |current_video_track_id_|
+    if (!web_stream_.IsNull()) {
+      blink::WebVector<blink::WebMediaStreamTrack> video_tracks;
+      web_stream_.VideoTracks(video_tracks);
+      DCHECK_GT(video_tracks.size(), 0U);
+      current_video_track_id_ = video_tracks[0].Id();
+    }
+  }
   // When associated with an <audio> element, we don't want to wait for the
   // first video fram to become available as we do for <video> elements
   // (<audio> elements can also be assigned video tracks).
@@ -288,6 +326,113 @@ void WebMediaPlayerMS::Load(LoadType load_type,
   }
 }
 
+void WebMediaPlayerMS::TrackAdded(const blink::WebMediaStreamTrack& track) {
+  Reload();
+}
+
+void WebMediaPlayerMS::TrackRemoved(const blink::WebMediaStreamTrack& track) {
+  Reload();
+}
+
+void WebMediaPlayerMS::Reload() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (web_stream_.IsNull())
+    return;
+
+  ReloadVideo();
+  ReloadAudio();
+}
+
+void WebMediaPlayerMS::ReloadVideo() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(!web_stream_.IsNull());
+  blink::WebVector<blink::WebMediaStreamTrack> video_tracks;
+  // VideoTracks() is a getter.
+  web_stream_.VideoTracks(video_tracks);
+
+  RendererReloadAction renderer_action = RendererReloadAction::KEEP_RENDERER;
+  if (video_tracks.IsEmpty()) {
+    if (video_frame_provider_)
+      renderer_action = RendererReloadAction::REMOVE_RENDERER;
+    current_video_track_id_ = blink::WebString();
+  } else if (video_tracks[0].Id() != current_video_track_id_) {
+    renderer_action = RendererReloadAction::NEW_RENDERER;
+    current_video_track_id_ = video_tracks[0].Id();
+  }
+
+  switch (renderer_action) {
+    case RendererReloadAction::NEW_RENDERER:
+      if (video_frame_provider_)
+        video_frame_provider_->Stop();
+
+      video_frame_provider_ = renderer_factory_->GetVideoRenderer(
+          web_stream_,
+          media::BindToCurrentLoop(
+              base::Bind(&WebMediaPlayerMS::OnSourceError, AsWeakPtr())),
+          frame_deliverer_->GetRepaintCallback(), io_task_runner_,
+          media_task_runner_, worker_task_runner_, gpu_factories_);
+      DCHECK(video_frame_provider_);
+      video_frame_provider_->Start();
+      break;
+
+    case RendererReloadAction::REMOVE_RENDERER:
+      video_frame_provider_->Stop();
+      video_frame_provider_ = nullptr;
+      break;
+
+    default:
+      return;
+  }
+
+  DCHECK_NE(renderer_action, RendererReloadAction::KEEP_RENDERER);
+  if (!paused_)
+    delegate_->DidPlayerSizeChange(delegate_id_, NaturalSize());
+}
+
+void WebMediaPlayerMS::ReloadAudio() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(!web_stream_.IsNull());
+  RenderFrame* const frame = RenderFrame::FromWebFrame(frame_);
+  if (!frame)
+    return;
+
+  blink::WebVector<blink::WebMediaStreamTrack> audio_tracks;
+  // AudioTracks() is a getter.
+  web_stream_.AudioTracks(audio_tracks);
+
+  RendererReloadAction renderer_action = RendererReloadAction::KEEP_RENDERER;
+  if (audio_tracks.IsEmpty()) {
+    if (audio_renderer_)
+      renderer_action = RendererReloadAction::REMOVE_RENDERER;
+    current_audio_track_id_ = blink::WebString();
+  } else if (audio_tracks[0].Id() != current_video_track_id_) {
+    renderer_action = RendererReloadAction::NEW_RENDERER;
+    current_audio_track_id_ = audio_tracks[0].Id();
+  }
+
+  switch (renderer_action) {
+    case RendererReloadAction::NEW_RENDERER:
+      if (audio_renderer_)
+        audio_renderer_->Stop();
+
+      audio_renderer_ = renderer_factory_->GetAudioRenderer(
+          web_stream_, frame->GetRoutingID(), initial_audio_output_device_id_,
+          initial_security_origin_);
+      audio_renderer_->SetVolume(volume_);
+      audio_renderer_->Start();
+      audio_renderer_->Play();
+      break;
+
+    case RendererReloadAction::REMOVE_RENDERER:
+      audio_renderer_->Stop();
+      audio_renderer_ = nullptr;
+      break;
+
+    default:
+      break;
+  }
+}
+
 void WebMediaPlayerMS::Play() {
   DVLOG(1) << __func__;
   DCHECK(thread_checker_.CalledOnValidThread());
@@ -394,6 +539,9 @@ bool WebMediaPlayerMS::HasAudio() const {
 
 blink::WebSize WebMediaPlayerMS::NaturalSize() const {
   DCHECK(thread_checker_.CalledOnValidThread());
+  if (!video_frame_provider_)
+    return blink::WebSize();
+
   if (video_rotation_ == media::VIDEO_ROTATION_90 ||
       video_rotation_ == media::VideoRotation::VIDEO_ROTATION_270) {
     const gfx::Size& current_size = compositor_->GetCurrentSize();