Report media track info from WebMediaPlayerMS

This CL makes sure audio and video tracks information are reflected in
HTMLMediaElement audioTracks and videoTracks when source is a MediaStream.

  Platform features" flag enabled.

Test: https://glowing-juvenile-bear.glitch.me/ with "Experimental Web
Bug: 894556
Change-Id: Iceac66b1f142d5c28eeaaffefd621c095e65ecda
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2518856Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Cr-Commit-Position: refs/heads/master@{#824360}

third_party/blink/renderer/modules/mediastream/webmediaplayer_ms.cc

@@ -475,28 +475,50 @@ WebMediaPlayer::LoadTiming WebMediaPlayerMS::Load(
     audio_renderer_->SetVolume(volume_);
     audio_renderer_->Start();
 
-    // Store the ID of audio track being played in |current_audio_track_id_|.
     if (!web_stream_.IsNull()) {
       MediaStreamDescriptor& descriptor = *web_stream_;
       auto audio_components = descriptor.AudioComponents();
+      // Store the ID of audio track being played in |current_audio_track_id_|.
       DCHECK_GT(audio_components.size(), 0U);
       current_audio_track_id_ = WebString(audio_components[0]->Id());
       SendLogMessage(String::Format("%s => (audio_track_id=%s)", __func__,
                                     current_audio_track_id_.Utf8().c_str()));
+      // Report the media track information to blink. Only the first audio track
+      // is enabled by default to match blink logic.
+      bool is_first_audio_track = true;
+      for (auto component : audio_components) {
+        client_->AddAudioTrack(
+            blink::WebString::FromUTF8(component->Id().Utf8()),
+            blink::WebMediaPlayerClient::kAudioTrackKindMain,
+            blink::WebString::FromUTF8(component->Source()->GetName().Utf8()),
+            /*language=*/"", is_first_audio_track);
+        is_first_audio_track = false;
+      }
     }
   }
 
   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()) {
       MediaStreamDescriptor& descriptor = *web_stream_;
       auto video_components = descriptor.VideoComponents();
+      // Store the ID of video track being played in |current_video_track_id_|.
       DCHECK_GT(video_components.size(), 0U);
       current_video_track_id_ = WebString(video_components[0]->Id());
       SendLogMessage(String::Format("%s => (video_track_id=%s)", __func__,
                                     current_video_track_id_.Utf8().c_str()));
+      // Report the media track information to blink. Only the first video track
+      // is enabled by default to match blink logic.
+      bool is_first_video_track = true;
+      for (auto component : video_components) {
+        client_->AddVideoTrack(
+            blink::WebString::FromUTF8(component->Id().Utf8()),
+            blink::WebMediaPlayerClient::kVideoTrackKindMain,
+            blink::WebString::FromUTF8(component->Source()->GetName().Utf8()),
+            /*language=*/"", is_first_video_track);
+        is_first_video_track = false;
+      }
     }
   }
   // When associated with an <audio> element, we don't want to wait for the

third_party/blink/web_tests/media/avtrack/audio-track-properties.html

@@ -22,6 +22,35 @@
                     assert_equals(audio.audioTracks[0].language, "", "audioTrack.language");
                 });
             });
+            async_test(function(t)
+            {
+                var ac1 = new AudioContext();
+                var stream1 = ac1.createMediaStreamDestination().stream;
+
+                var ac2 = new AudioContext();
+                var stream2 = ac2.createMediaStreamDestination().stream;
+
+                var audio = document.createElement("audio");
+                var tracks = [...stream1.getTracks(), ...stream2.getTracks()];
+                var stream = new MediaStream(tracks);
+                audio.srcObject = stream;
+                audio.onloadedmetadata = t.step_func_done(function()
+                {
+                    assert_equals(audio.audioTracks.length, 2, "audioTracks.length");
+
+                    assert_true(audio.audioTracks[0].enabled, "audioTrack.enabled");
+                    assert_true("id" in audio.audioTracks[0], "audioTrack.id");
+                    assert_equals(audio.audioTracks[0].kind, "main", "audioTrack.kind");
+                    assert_true("label" in audio.audioTracks[0], "audioTrack.label");
+                    assert_equals(audio.audioTracks[0].language, "", "audioTrack.language");
+
+                    assert_false(audio.audioTracks[1].enabled, "audioTrack.enabled");
+                    assert_true("id" in audio.audioTracks[1], "audioTrack.id");
+                    assert_equals(audio.audioTracks[1].kind, "main", "audioTrack.kind");
+                    assert_true("label" in audio.audioTracks[1], "audioTrack.label");
+                    assert_equals(audio.audioTracks[1].language, "", "audioTrack.language");
+                });
+            });
         </script>
     </body>
 </html>

third_party/blink/web_tests/media/avtrack/video-track-properties.html

@@ -22,6 +22,37 @@
                     assert_equals(video.videoTracks[0].language, "", "videoTrack.language");
                 });
             });
+            async_test(function(t)
+            {
+                var canvas1 = document.createElement("canvas");
+                canvas1.getContext('2d').fillRect(0, 0, canvas1.width, canvas1.height);
+                var stream1 = canvas1.captureStream();
+
+                var canvas2 = document.createElement("canvas");
+                canvas2.getContext('2d').fillRect(0, 0, canvas2.width, canvas2.height);
+                var stream2 = canvas2.captureStream();
+
+                var video = document.createElement("video");
+                var tracks = [...stream1.getTracks(), ...stream2.getTracks()];
+                var stream = new MediaStream(tracks);
+                video.srcObject = stream;
+                video.onloadedmetadata = t.step_func_done(function()
+                {
+                    assert_equals(video.videoTracks.length, 2, "videoTracks.length");
+
+                    assert_true(video.videoTracks[0].selected, "videoTrack.selected");
+                    assert_true("id" in video.videoTracks[0], "videoTrack.id");
+                    assert_equals(video.videoTracks[0].kind, "main", "videoTrack.kind");
+                    assert_true("label" in video.videoTracks[0], "videoTrack.label");
+                    assert_equals(video.videoTracks[0].language, "", "videoTrack.language");
+
+                    assert_false(video.videoTracks[1].selected, "videoTrack.selected");
+                    assert_true("id" in video.videoTracks[1], "videoTrack.id");
+                    assert_equals(video.videoTracks[1].kind, "main", "videoTrack.kind");
+                    assert_true("label" in video.videoTracks[1], "videoTrack.label");
+                    assert_equals(video.videoTracks[1].language, "", "videoTrack.language");
+                });
+            });
         </script>
     </body>
 </html>