[M114] Move transceiver iteration loop over to the signaling thread.

This is required for ReportTransportStats since iterating over the
transceiver list from the network thread is not safe.

(cherry picked from commit dba22d3)

No-Try: true
Bug: chromium:1446274, webrtc:12692
Change-Id: I7c514df9f029112c4b1da85826af91217850fb26
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/307340
Reviewed-by: Harald Alvestrand <[email protected]>
Commit-Queue: Tomas Gunnarsson <[email protected]>
Cr-Original-Commit-Position: refs/heads/main@{#40197}
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/308001
Reviewed-by: Mirko Bonadei <[email protected]>
Cr-Commit-Position: refs/branch-heads/5735@{#3}
Cr-Branched-From: df7df19-refs/heads/main@{#39949}

Author: Tommi

pc/peer_connection.cc

@@ -735,9 +735,6 @@ JsepTransportController* PeerConnection::InitializeTransportController_n(
   transport_controller_->SubscribeIceConnectionState(
       [this](cricket::IceConnectionState s) {
         RTC_DCHECK_RUN_ON(network_thread());
-        if (s == cricket::kIceConnectionConnected) {
-          ReportTransportStats();
-        }
         signaling_thread()->PostTask(
             SafeTask(signaling_thread_safety_.flag(), [this, s]() {
               RTC_DCHECK_RUN_ON(signaling_thread());
@@ -2401,6 +2398,20 @@ void PeerConnection::OnTransportControllerConnectionState(
     case cricket::kIceConnectionConnected:
       RTC_LOG(LS_INFO) << "Changing to ICE connected state because "
                           "all transports are writable.";
+      {
+        std::vector<RtpTransceiverProxyRefPtr> transceivers;
+        if (ConfiguredForMedia()) {
+          transceivers = rtp_manager()->transceivers()->List();
+        }
+
+        network_thread()->PostTask(
+            SafeTask(network_thread_safety_,
+                     [this, transceivers = std::move(transceivers)] {
+                       RTC_DCHECK_RUN_ON(network_thread());
+                       ReportTransportStats(std::move(transceivers));
+                     }));
+      }
+
       SetIceConnectionState(PeerConnectionInterface::kIceConnectionConnected);
       NoteUsageEvent(UsageEvent::ICE_STATE_CONNECTED);
       break;
@@ -2743,20 +2754,18 @@ void PeerConnection::OnTransportControllerGatheringState(
 }
 
 // Runs on network_thread().
-void PeerConnection::ReportTransportStats() {
+void PeerConnection::ReportTransportStats(
+    std::vector<RtpTransceiverProxyRefPtr> transceivers) {
   TRACE_EVENT0("webrtc", "PeerConnection::ReportTransportStats");
   rtc::Thread::ScopedDisallowBlockingCalls no_blocking_calls;
   std::map<std::string, std::set<cricket::MediaType>>
       media_types_by_transport_name;
-  if (ConfiguredForMedia()) {
-    for (const auto& transceiver :
-         rtp_manager()->transceivers()->UnsafeList()) {
-      if (transceiver->internal()->channel()) {
-        std::string transport_name(
-            transceiver->internal()->channel()->transport_name());
-        media_types_by_transport_name[transport_name].insert(
-            transceiver->media_type());
-      }
+  for (const auto& transceiver : transceivers) {
+    if (transceiver->internal()->channel()) {
+      std::string transport_name(
+          transceiver->internal()->channel()->transport_name());
+      media_types_by_transport_name[transport_name].insert(
+          transceiver->media_type());
     }
   }
 

pc/peer_connection.h

@@ -569,7 +569,8 @@ class PeerConnection : public PeerConnectionInternal,
 
   // Invoked when TransportController connection completion is signaled.
   // Reports stats for all transports in use.
-  void ReportTransportStats() RTC_RUN_ON(network_thread());
+  void ReportTransportStats(std::vector<RtpTransceiverProxyRefPtr> transceivers)
+      RTC_RUN_ON(network_thread());
 
   // Gather the usage of IPv4/IPv6 as best connection.
   static void ReportBestConnectionState(const cricket::TransportStats& stats);

pc/peer_connection_integrationtest.cc

@@ -1831,6 +1831,10 @@ TEST_P(PeerConnectionIntegrationTest,
   EXPECT_EQ_WAIT(webrtc::PeerConnectionInterface::kIceConnectionConnected,
                  callee()->ice_connection_state(), kDefaultTimeout);
 
+  // Part of reporting the stats will occur on the network thread, so flush it
+  // before checking NumEvents.
+  SendTask(network_thread(), [] {});
+
   EXPECT_METRIC_EQ(1, webrtc::metrics::NumEvents(
                           "WebRTC.PeerConnection.CandidatePairType_UDP",
                           webrtc::kIceCandidatePairHostNameHostName));
@@ -1959,6 +1963,10 @@ TEST_P(PeerConnectionIntegrationIceStatesTest, MAYBE_VerifyBestConnection) {
   EXPECT_EQ_WAIT(webrtc::PeerConnectionInterface::kIceConnectionConnected,
                  callee()->ice_connection_state(), kDefaultTimeout);
 
+  // Part of reporting the stats will occur on the network thread, so flush it
+  // before checking NumEvents.
+  SendTask(network_thread(), [] {});
+
   // TODO(bugs.webrtc.org/9456): Fix it.
   const int num_best_ipv4 = webrtc::metrics::NumEvents(
       "WebRTC.PeerConnection.IPMetrics", webrtc::kBestConnections_IPv4);