Surface associated remote stream MSID changes for active receivers.

Previously, associated media streams were only updated on the
"addition" and "removal" of a track. But MSIDs can change for active
receivers as well. In this CL, we always update the associated media
streams based on the state of the webrtc-layer receiver.

Bug: webrtc:10083
Change-Id: I54bb00a5077a0b7b78964faf13882055c8101427
Reviewed-on: https://chromium-review.googlesource.com/c/1384257
Commit-Queue: Henrik Boström <hbos@chromium.org>
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618333}

third_party/blink/renderer/modules/peerconnection/rtc_peer_connection.cc

@@ -2666,16 +2666,30 @@ void RTCPeerConnection::DidModifyTransceivers(
     RTCRtpTransceiver* transceiver =
         CreateOrUpdateTransceiver(std::move(web_transceiver));
 
-    // The transceiver is now up-to-date. Compare before/after values of
-    // FiredDirectionHasRecv() and process the remote track if it changed.
-    if (is_remote_description && !previously_had_recv &&
-        transceiver->FiredDirectionHasRecv()) {
-      ProcessAdditionOfRemoteTrack(
-          transceiver, transceiver->web_transceiver()->Receiver()->StreamIds(),
-          &add_list, &track_events);
+    size_t add_list_prev_size = add_list.size();
+    // "Set the associated remote streams".
+    // https://w3c.github.io/webrtc-pc/#set-associated-remote-streams
+    SetAssociatedMediaStreams(
+        transceiver->receiver(),
+        transceiver->web_transceiver()->Receiver()->StreamIds(), &remove_list,
+        &add_list);
+    // The transceiver is now up-to-date. Check if the receiver's track is now
+    // considered added or removed (though a receiver's track is never truly
+    // removed). A track event indicates either that the track was "added" in
+    // the sense that FiredDirectionHasRecv() changed, or that a new remote
+    // stream was added containing the receiver's track.
+    if (is_remote_description &&
+        ((!previously_had_recv && transceiver->FiredDirectionHasRecv()) ||
+         add_list_prev_size != add_list.size())) {
+      // "Process the addition of a remote track".
+      // https://w3c.github.io/webrtc-pc/#process-remote-track-addition
+      track_events.push_back(transceiver);
     }
     if (previously_had_recv && !transceiver->FiredDirectionHasRecv()) {
-      ProcessRemovalOfRemoteTrack(transceiver, &remove_list, &mute_tracks);
+      // "Process the removal of a remote track".
+      // https://w3c.github.io/webrtc-pc/#process-remote-track-removal
+      if (!transceiver->receiver()->track()->muted())
+        mute_tracks.push_back(transceiver->receiver()->track());
     }
   }
   MediaStreamVector current_streams = getRemoteStreams();
@@ -2741,29 +2755,6 @@ void RTCPeerConnection::DidModifyTransceivers(
   }
 }
 
-void RTCPeerConnection::ProcessAdditionOfRemoteTrack(
-    RTCRtpTransceiver* transceiver,
-    const WebVector<WebString>& stream_ids,
-    HeapVector<std::pair<Member<MediaStream>, Member<MediaStreamTrack>>>*
-        add_list,
-    HeapVector<Member<RTCRtpTransceiver>>* track_events) {
-  SetAssociatedMediaStreams(transceiver->receiver(), stream_ids, nullptr,
-                            add_list);
-  track_events->push_back(transceiver);
-}
-
-void RTCPeerConnection::ProcessRemovalOfRemoteTrack(
-    RTCRtpTransceiver* transceiver,
-    HeapVector<std::pair<Member<MediaStream>, Member<MediaStreamTrack>>>*
-        remove_list,
-    HeapVector<Member<MediaStreamTrack>>* mute_tracks) {
-  WebVector<WebString> stream_ids = {};
-  SetAssociatedMediaStreams(transceiver->receiver(), stream_ids, remove_list,
-                            nullptr);
-  if (!transceiver->receiver()->track()->muted())
-    mute_tracks->push_back(transceiver->receiver()->track());
-}
-
 void RTCPeerConnection::SetAssociatedMediaStreams(
     RTCRtpReceiver* receiver,
     const WebVector<WebString>& stream_ids,

third_party/blink/renderer/modules/peerconnection/rtc_peer_connection.h

@@ -405,19 +405,6 @@ class MODULES_EXPORT RTCPeerConnection final
   RTCRtpTransceiver* CreateOrUpdateTransceiver(
       std::unique_ptr<WebRTCRtpTransceiver>);
 
-  // https://w3c.github.io/webrtc-pc/#process-remote-track-addition
-  void ProcessAdditionOfRemoteTrack(
-      RTCRtpTransceiver* transceiver,
-      const WebVector<WebString>& stream_ids,
-      HeapVector<std::pair<Member<MediaStream>, Member<MediaStreamTrack>>>*
-          add_list,
-      HeapVector<Member<RTCRtpTransceiver>>* track_events);
-  // https://w3c.github.io/webrtc-pc/#process-remote-track-removal
-  void ProcessRemovalOfRemoteTrack(
-      RTCRtpTransceiver* transceiver,
-      HeapVector<std::pair<Member<MediaStream>, Member<MediaStreamTrack>>>*
-          remove_list,
-      HeapVector<Member<MediaStreamTrack>>* mute_tracks);
   // Update the |receiver->streams()| to the streams indicated by |stream_ids|,
   // adding to |remove_list| and |add_list| accordingly.
   // https://w3c.github.io/webrtc-pc/#set-associated-remote-streams

third_party/blink/web_tests/TestExpectations

@@ -3235,7 +3235,6 @@ crbug.com/893480 external/wpt/infrastructure/testdriver/actions/elementTiming.ht
 crbug.com/893480 external/wpt/infrastructure/testdriver/actions/multiDevice.html [ Failure Timeout ]
 
 # ====== New tests from wpt-importer added here ======
-crbug.com/626703 virtual/webrtc-wpt-unified-plan/external/wpt/webrtc/RTCTrackEvent-fire.html [ Timeout ]
 crbug.com/626703 external/wpt/css/filter-effects/filter-subregion-01.html [ Failure ]
 crbug.com/626703 external/wpt/webrtc/RTCTrackEvent-fire.html [ Timeout ]
 crbug.com/626703 virtual/layout_ng_experimental/external/wpt/css/css-multicol/multicol-span-all-005.html [ Failure ]